Wear protective equipment and watch out for low wires or stuff like that. I'm not going to say don't go 100k's, because I'm sure that's fun, but you have to think safety. I knew of someone that was killed on a snowmobile when he ran into a cable.
Unless you are on a snowmobile speed course, 100mph is insane, so my tip would be don't do it. If you are on a speed course, take tips from the professionals familiar with that course.