d1: i think d1 has a focus on personal training; often these personal trainers will teach skills like jewelry making/instrument making/etc so it doubles as an apprenticeship for a future profession AND training for the games. additionally these trainers will also tutor children in a potential victor talent — singing, dancing, playing piano, etc. children begin training after school as soon as they enter school, and their spot with a trainer is either paid for by their parents or they are scouted at a yearly, school-sponsored event called field day. in the case of the scouted tribute, often their tesserae will be taken out and given to the scout as compensation. trainers rarely take on more than one tribute at once; on the rare occasion they do it will be like, an 11/12 year old and an 18 year old. once the tributes are older, (16/17) there will be a few months where they're going through ‘partner tryouts’ to test the chemistry and compatibility between male and female potential tributes. these don't necessarily have to be positive relationships, as tributes that dislike each other can still play off each other well in the arena & bring in more sponsor gifts, but a pair that is disinterested in each other doesn't look great on the cameras. after partner tryouts, sometimes trainers will decide to spend an afternoon or two each week training their tributes together, but not always. volunteers are selected by whichever those citizens in the square cheered loudest for when they volunteered. (hc vaguely inspired by mollywog's post here)
d2: d2 is the only district that has a formal “academy" of sorts. most similar to a military academy, this is district two's largest school; largely it focuses on producing peacekeepers; around a dozen or so 12 year old trainees each year are selected for special training which involves studying games strategy, hand-to-hand combat, and medical skills. those who make it all the way through this without being selected as tribute will often be assigned a commanding role or go into the medical track of the peacekeepers (becoming a district doctor, etc). tributes are selected when the top five (chosen via scores and a committee of instructors) are given to the mentors; the mentors that year pick what tribute they want to mentor. because of the academy system, all children take the maximum amount of tesserae, but the only children who receive them are children who are in the academy. children of quarry workers often leave the academy at 16 to work in the quarry rather than continue on and become a peacekeeper. there are other schools in district two, but they're much smaller and mostly filled with quarry workers' children rather than the children of retired peacekeepers. similar to district one, 17 year old potential tributes will have partner tryouts to see who works the best together; these assigned pairings will spend a lot of time training together over the next year to ensure they work well together and together they can give district two the best chance of winning. mentors CAN pick tributes who haven't been assigned together, but it doesn't happen often, and is usually due to an injury or some other unexpected event. tributes are usually told the morning of that they are the volunteer (in the rare case of a situation with multiple volunteers, they will play back the recording to see who “really” volunteered first. this is unlikely as it is seen as extremely dishonorable to volunteer if you are not the pre-selected tribute, but has happened).
d4: the “academy” here is really the community home. children who live in the community home do group exercise in the morning or at night from a young age (older children can be given dispensation to work instead) and it is expected that one of them will volunteer if a younger or more incapable tribute is called, as their way of repaying their district for feeding/housing/raising them. this doesn't always happen (hence: finnick going in at 14). this also prepares them for life after the community home (making them into fit, able workers who are more likely to be able to get a job on a fishing boat instead of in a cannery or a desalination plant. this district has the “complicated” volunteering, with cases of multiple volunteers involving rushing to the stage, and whichever tribute touches the stage first is the official volunteer.
d10: while there is no expectation of volunteering in 10 (hence katniss leaving it off her list of career districts), district ten has a very community oriented attitude, and their well-prepared tributes often end up joining the pack. children are funnelled into sports from the time they start school (boxing, wrestling, track) and thus are more prepared than other districts. similarly to four, children also are permitted with dispensation to enter the work force early, which can also lend them an advantage in the arena.
