I LOVE Percherons, and my stable has about ten of them, so I hang out with the big boys as often as I can. Just remember - Percherons can get very, VERY big, and are not always gentle, as Solon has pointed out. Some are also very head shy, and thats due to neglect or misuse in the past. When you first get your horse you need to be watchful for little things that might set him off. For instance, I went to pick out a hoof of one of the drafts, and he started bucking right then and there, in the cross ties. One of his hooves struck me and I had to go into the hospital to make sure nothing was wrong.
Also, I don't suggest mounting until you are familiar with the horse. I like to give it a week or so before mounting a new horse, because I want to establish trust in our relationship.
I've seen so many Drafts injured by being forced into trailers that are too small for them. Percherons can get very big, and if you plan to trailer him often, make sure he will be comfortable and not too cramped in your trailer.
DON'T spoil him with treats. This teaches him bad habits. If he was mistreated in the past, and you immediately start cramming treats down his throat, the horse can get unruly and take charge. Believe me, you do NOT want a 1000+ pound animal thinking he's boss!
Hope this helped!