I would buy a 250F or 2 stroke 250 for your first bike. 450s can be a handful for an inexperienced rider. If your heart is set on the 450, then the best thing you can do is TAKE IT EASY!! Learn how to ride in a field first. Learn how the bike behaves compared to your quad. Take it on some trails and learn how to ride on a variety of terrain. After a few months of practice, you'll be riding it like it's your quad.