I'm very much a beginner, but thought I'd tell you about my experience. Last year we threw stuff in the ground and didn't do anything to them. We had 3 tomato plants. They grew like MAD, and weren't caged or pruned at all. We just let them do what they wanted to. They ended up looking like a bush, all round. We had a TON of tomatoes from them. When they were full of fruit they started to fall a bit, we did eventually put a couple of stakes up to help them out. So, from that experience I would say if you just don't stake or cage them they would naturally grow this way.
I'm sure some others will have much more information for you.