This is a list of all of the tasks Link can accomplish as part of the Bombers' Notebook side-quest in The Legend of Zelda: Majora's Mask.
Spoiler warning: Plot or ending details follow.
Bombers Secret Society of Justice[]
24 hours a day, Jim will be shooting at the balloon of Majora's Mask in North Clock Town. To join the Bombers Society and earn their secret password and Bombers' Notebook, Link may play Hide-and-Seek with the group to pass their test. Once he does, he will be taught a code that will enable him to enter the Bombers' Hideout, leading to the Astral Observatory in East Clock Town. If he goes back in time to the dawn of the First Day, the code will remain be the same and he can enter their hideout.
Anju/Kafei[]
To begin this task, Link should be in the lobby of the Stock Pot Inn between 1:50 and 4:00 p.m. on the First Day. When Anju returns from bringing lunch to her grandmother, Link can speak to her; when she asks if he has a reservation, all he has to do is say "yes". For some reason, he actually does. He will receive the Room Key to the Knife Chamber at the inn and the happiness seal that indicates the missive is complete.
After receiving Kafei's Mask from Kafei's mother, Link should return to the Stock Pot Inn. Between 2:30 and 7:50 p.m., he should speak to Anju while wearing the mask. This will show her that Link is searching for Kafei, and she will ask him to meet her secretly at 11:30 that night in the inn's kitchen.
When Link attends the requested meeting with Anju, she will explain that she is engaged to Kafei and provide information about his disappearance. She will then give Link a Letter to Kafei and ask him to mail it for her, as she is afraid to do it herself. Link can do this at any time during the night or the next morning by placing the letter into any postbox in town.
Link must be at the Laundry Pool at 3:25 p.m. on the Second Day. The Postman will deliver the Letter to Kafei, the one that Link posted for Anju. When Kafei exits the Backroom to retrieve it, Link can run into the unlocked room to wait for him. After Kafei removes his mask, he will tell Link about the thief who stole his wedding mask, then give him the Pendant of Memories, which Link must deliver to Anju. The pendant will remind Anju of the happiness that she and Kafei shared in the past, and she will agree to wait for him.
In order for this to work, Link must not prevent the robbery of the Old Lady from the Bomb Shop; the bombs must be stolen or this part cannot proceed. After the pendant is in Anju's hands, Link should head for Ikana Canyon; he absolutely must be there by 6:00 p.m. to achieve the next goal, and getting there early is strongly advised. Showing the Garo's Mask to the Ghost Hunter will enable Link to go up the steep cliff, and at the end of the Road to Ikana is Sakon's Hideout. There he will find Kafei, hiding behind some rocks to the left of the entrance and waiting for Sakon to return. Link must also hide before Sakon arrives. Once he does, and opens his hideout, Kafei will run inside and Link must follow.
This is a complicated series of events in which Link and Kafei take turns being the active "performer". Kafei accidentally causes his stolen mask to start moving on a conveyor belt toward where Sakon is waiting, and he and Link must work together to get it before it reaches the end of the belt. In the first room, Kafei should push one of the blocks onto the switch to open the door for Link, who must defeat the Deku Baba near the exit. Kafei should avoid the red switches, which will speed up the conveyor belt; the blue one will open the door. Any yellow switches will slow the conveyor belt. Again Link must dispatch the Deku Baba he finds. Kafei must then rearrange blocks; the farthest left block in the top row should be moved to the right, then he must pull the farthest left block in the middle row backwards. He can then go down and step on the switch, and Link can defeat the Wolfos he finds there. Kafei should then step on the lower switch to open a door for Link. Link can then stay on the upper switch to block the hole at the end of the conveyor belt. Kafei can then grab the mask.
Once Link has helped Kafei regain the Sun's Mask, he can use his Ocarina of Time to warp back to Clock Town and travel to the Stock Pot Inn. All he needs to do there is enter the Employees Room upstairs, where Anju is waiting for Kafei; Link should wait with her. When Kafei arrives, he and Anju combine their Sun's and Moon's Masks just as they would have at their wedding. They then give the completed Couple's Mask to Link.
Man from the Curiosity Shop[]
During the afternoon on the Final Day, the Man from the Curiosity Shop will be waiting in the Backroom, accessible from the Laundry Pool. If Link has received the Pendant of Memories from Kafei, he may enter the Backroom, where the the man will talk to him about his history with Kafei. He will also give Link the Keaton Mask and the Letter to Mama.
Link can also buy the All-Night Mask from him during night of the Final Day, only if he prevented Sakon from stealing the Bomb Bag from the Old Lady from Bomb Shop during night of the First Day.
Old Lady from Bomb Shop[]
At midnight on the First Day, Old Lady from Bomb Shop will be making her way through North Clock Town with a bag of bombs. She will be robbed by Sakon, and Link may chase him and hit him with his sword to make him drop the bag. If he stops Sakon from getting away, the Old Lady will reward him with the Blast Mask.
Romani[]
At 2:30 a.m. during the First Day, Romani will enter the barn of Romani Ranch to protect the cows from "Them". If Link has obtained the Hero's Bow from Woodfall Temple and obtained a Powder Keg from Goron Village, he may enter the ranch by detonating the Powder Keg next to the boulder blocking the path. Link may speak with Romani who will ask him to be her assistant. If he obliges her, he can practice shooting balloons around the ranch in preparation for the attack on the ranch. After successfully popping the balloons, Romani will teach Link "Epona's Song", which will let him summon Epona at any point during any three-day cycle. If Link stops "Them" from attacking until dawn of the next morning, Romani will thank Link and give him a bottle filled with Milk.
Cremia[]
If the cows from Romani Ranch have not been abducted, at 6:00 p.m. on the Second Day, Cremia will be taking a carriage of milk to Clock Town. Link may ask her for a ride, and she will talk to him while leaving the ranch about her troubles. As they enter Milk Road, Cremia will warn Link to ready his bow, as they must detour through "ugly country." During the ride through the detour, the carriage will be chased and attacked by the Gorman Brothers riding horses. If Link successfully keeps them away with arrows, Cremia will reward him with Romani's Mask.
Mayor Dotour[]
From 10 a.m. until 8 p.m. on the First and Second days, Mayor Dotour is stuck in a very long meeting in his office with Mutoh and his carpenters, and Captain Viscen and some soldiers. If Link dons the Couple's Mask and speaks to the mayor, the meeting will end. Mayor Dotour is so relieved that he rewards Link with a Piece of Heart.
Madame Aroma[]
This is one of the simplest tasks in the notebook. Link must go to the Mayor's Residence and speak with his wife, Madame Aroma. She will ask Link to help find her missing son, Kafei. To help him in his search, she gives Link Kafei's Mask; he can show other people that he is searching for Kafei by putting on the mask, and they will provide him with clues.
At the same time that Link receives the Keaton Mask at the Curiosity Shop, he will also be given a letter to deliver to Madame Aroma. Link should wait until evening, after 6:00 p.m., then go to the Milk Bar to find her. If he puts on Kafei's Mask, she will remember that she sent him to find her lost son, at which time he can give her the letter. She will be so happy to have word from Kafei that she will reward Link with a bottle of Chateau Romani.
Toto/Gorman[]
Link can perform this task between 10:00 p.m. and 6:00 a.m. on either the First or the Second Day. In order to do it, he will need the Deku Mask, the Goron Mask, the Zora Mask, and Romani's Mask, which will get him in the door. Inside he will meet Toto, who wonders how the performance would have gone if everyone weren't trying to flee. Link should wear each of the masks in turn to talk to him, then follow his directions to play music onstage. The completed song is the "Ballad of the Wind Fish"; Gorman, who is at the bar, will be touched by it and give Link the Circus Leader's Mask in gratitude.
Postman[]
Any time between 3:00 p.m. and midnight on either the First or Second Day, Link can go to the post office to play Mental Training with the Postman. The Postman tries to determine when ten seconds have elapsed without looking at the clock. This is mostly a matter of trial and error, although subsequent attempts will cost Link two Rupees each time. If Link can stop the timer at exactly 10:00, the Postman will give him a Piece of Heart. Wearing the Bunny Hood shows the timer, and slowing down time makes the timer go slower, making it easier.
Instead of delivering the letter to Madame Aroma himself, Link can have the Postman do it, which is the only way to complete this task. If Link goes to the Post Office, he will find the Postman wishing he could leave town. When Link gives him the letter, he will see the priority seal on it and go to deliver it immediately; Link should follow him to the Milk Bar. After Madame Aroma reads the letter, she will advise the Postman to flee the town, and he will give Link his hat.
Rosa Sisters[]
This task can only be completed after Link has received Kamaro's Mask. He should then head to West Clock Town, between 6:00 p.m. and 6:00 a.m. on the First or the Second Day. There, he will meet the Rosa Sisters, who are practicing their rather dismal dance moves. If Link puts on Kamaro's Mask, he can teach them a better routine, which they will love so much that they give him a Piece of Heart.
???[]
??? lives in the Stock Pot Inn's toilet and only comes out at midnight to grab some toilet paper. Since there is none, Link can give him a letter or other document, such as any of the Title Deeds or the Letter to Mama, to get the job done. In return for this kindness, Link will receive a Piece of Heart. To accomplish this task, Link must be in the hotel, either by acquiring the Room Key or by hovering to it with a Deku Flower.
Anju's Grandmother[]
This covers two separate tasks. Anju's Grandmother is apparently not the most riveting of orators, and Link will normally fall asleep if he listens to her read a story. If Link dons the All-Night Mask, he can stay awake throughout either story. Link must then request that she read the "Carnival of Time" story. If Link answers her question correctly at the end, she will give him a Piece of Heart. Link can earn another Piece of Heart in the same way, by asking her to read the "Four Giants" story, then answering "I don't know" to her question at the end. These tasks can be performed any time between 8:00 a.m. and noon on either the First or the Second Day.
Kamaro[]
On any of the three days, between midnight and 6:00 a.m., Link should head to northern Termina Field, near the entrance to Snowhead. There he will find the dancer Kamaro, who will talk to Link about his troubled spirit. All Link needs to do is play the "Song of Healing" on his Ocarina of Time, and Kamaro will thank him by giving him Kamaro's Mask.
Grog[]
Within Romani Ranch, Link can find the Cucco Shack where Grog raises Cuccos. He would like to see them reach their adult stage before the Moon crashes into Termina and destroys everything. Link can help him if he has received the Bremen Mask from Guru-Guru; all he has to do is put it on and start marching around. The Cuccos will start to follow him. Once he has them all marching behind him, they will speed up their growth and become adults. Grog will be so pleased with this, he will give Link the Bunny Hood as thanks.
Gorman Brothers[]
After Link has Epona from Romani Ranch, he should ride her down Milk Road to the Gorman Brothers' racing track. If he speaks to the older brother while sitting on her back, the brother will challenge Link to a horse race. Once Link wins, the brothers will reluctantly give him the Garo's Mask as a prize.
Shiro[]
Shiro the soldier has been in Ikana Canyon for some time. Link can go to see him any time after he has Epona; the only problem is that he is invisible. Link will need to use the Lens of Truth in order to see him. Shiro is badly injured, so Link must give him some Red Potion or Blue Potion to heal his wounds. Afterwords, they will find that the reason for Shiro's invisibility is the fact that he's owns the Stone Mask, which makes someone invisible, so he gives it to Link.
Guru-Guru[]
Guru-Guru is a musician whose performances were too loud for the Stock Pot Inn. Link can find him at the Laundry Pool instead, between 6:00 p.m. and 6:00 a.m. on either the First or the Second Day. Guru-Guru will speak openly with Link because they are alone. If Link will be patient and listen to his story all the way to its end, Guru-Guru will thank him by giving him the Bremen Mask.
Spoiler warning: Spoilers end here.