If the compounds you shot belong to friends, talk to them. If not, go to a pro shop and talk to them (find one you have confidence in).
Most of them will allow you to try a variety of bows to get one you like and that fits you. They will also help you with the initial set-up of the bow (setting nock height, tying in peep sights, tying on string loops, etc.).

If you order one from Cabelas or Bass Pro, you'll have to do all this yourself (which can be a little overwhelming at first) or pay someone else to do it. A well cared for used bow is also a good option but, if it is already set -up for someone else, it might not fit you, exactly, and you're back to square one.

The pro shop bow might cost a little more (might not) but, if you don't have knowledgable friends who can get you pointed in the right direction, it will save you a lot of headaches with your first bow.

Last thought. Don't scrimp on arrows. If you have good arrows you can shoot well with any bow but, if you have junk arrows, the best bow out there won't group them.