Special considerations: remember he's a horse, not a dog ;) Many people don't treat minis as actual horses due to their size. But, just like the big guys, they're still horses :) Still need feet trimmed (usually more frequently than large horses since they don't wear down their hooves as much), worming (to their size, and do NOT use Quest), shots (same dose as a large horse). Also make sure not to overfeed! Minis weigh an average of 250 pounds or so, more or less depending on size. Feed accordingly ;) They're easy keepers in that regard!
As for the mane... agree with the other poster, that is TOTALLY up to the owner. I do NOT touch mine's manes other than the bridle path. They're fuzzy, too, but for shows I just use conditioner, put a sleazy on while still damp, then in the AM they're nice and slick, and I use hair gel on stubborn hairs. But anyhow, here is what's done to mini's manes:
Bridle paths are longer on minis, think of arabs. See the mini in my sig? Many people do a bigger bridle path than that, but I don't. I don't do much of one on Chili, my combined driving mini. For showing, many people want less mane, so they will also SHAVE the underside of the mane off, sometimes some of the top, too. I refuse, I think it's stupid, but that's just me ;) I also refuse to razor off their whiskers and the hair on their nose and around their eyes, but many people like that look and so they do it... But since I don't think you're showing this guy(?) you don't have to even think about that ;)
Oh, and minis grow a massive winter coat. Hands on at least weekly to FEEL the weight. I personally have shaved mine for show only to discover they were thinner (though not skinny) than I thought... That fuzzy coat can fool you! :)
Is the mini mare, gelding, or stallion? If a stallion, keep in mind, just b/c they're smaller, they aren't any less of a stallion. They are usually really sweet with people but still, they are a stallion and they KNOW it! Hubby's 23 y/o stallion is one of the calmest, easiest going horses we have... but walk him past the girls and he's prancing, squealing, the whole 9 yards! LOL
Jessi