Yeah, I agree with you. 你好 sounds formal and not so close when used between friends. You can say '你最近怎么样?' (How is it going with you?) but not just '怎么样'.
First, '怎么样' is used for asking opinions. E.g. You try on a shirt and ask others how they think of it, just say 怎么样?
Second, it's also used to ask how things go on. E.g. Your son finished a test. If you just wait outside the eaxming room and he goes out, you can just say 怎么样?.
But if it isn't so clear about what you are asking for opinions, add the thing before 怎么样, like 测试怎么样?(=How was your test?) The same with the shirt mentioned before.
Any further question is welcome.