MIEventer (Trakehner): I would approach one at a collected canter. I know that may seem a little slow, but I am thinking about the upbeat, uphill, canter. This way your horse is paying more attention to you, and will most likely hit the jump more accurate. Remember to sink in your heels, and keep your eyes focused on something up ahead. But you probably don't need me to tell you this (I know you already know :) )
MIEventer: I am only a Novice level eventer. Although I am not at the most advanced eventing level, I have a green horse. Also I am booksmart (Pony Club), which is the whole reason I opened this thread in the first place. To share my knowledge from eventing and Pony Club, combined with the answers of others to help more people learn about eventing.
Spastic Dove (coffin canter): The coffin canter is very similar to the collected upbeat canter I was talking about with MIEventer. It is a collected canter used to help you approach and takeoff at the ditch in a coffin jump correctly. A coffin canter is important, because of the way a coffin jump is constructed- You need to stay calm, supple, and collected, in order to reach all three parts correctly and accurately.
Hope this helps! E