Question: I'm making a game with target (orbit camera). I want to limit camera movements when in room. So that camera don't go through walls when moving around target and along the ground.
What are common approaches? Any good links with tutorials? I use Unity3D, nevertheless I'm good with a general solution to the problem

Answer: 
Go to LudumDare and see games that got a lot of positive attention in previous competitions. Play them and see which ones you like and simply develop on those ideas. Taking ideas from one game is stealing, taking from two or more is research.
I disagree with @William 'MindWorX' Mariager regarding the nature of the question. It's game design and game programming related and belong here. 

@Tomas, you created the egg before the chicken. You want your coding to have a purpose first. This is how project and business works. Most game development team will create the game design (most of it)(like a Game Design Document) before starting the programming of the game. 

My studio has the inverse problem. We got a large amount of viable ideas, largely documented, and no game engine, modules or programmers to run/code it. I am even considering learning coding myself instead of waiting for the arrival of a miraculous coder.

I remember my first game idea. I was playing a Zynga game on Facebook and I thought: "The game is okay, but it could be more fun" and then: "I could easily create a better game than this". Shortly after, I started creating it. I suggest you think about what game you could improve (without copying or breaching copyrights) and start focusing on this with your game engine.

Also, try using brainstorm technics to stimulate and generate ideas and innovation.