Just find out the names of games developers and get their address. Then write to them nicely explaining that you have some ideas and if they wish they could read them and maybe speak to you about them. I'm sure they get alot of people doing that though.
You kinda really need to study a specific course at university though, then hope to be taken on by a company when you get your degree. Some companies might take placements whilst you're studying, so research which course might put you into a placement scheme as soon as, then you've got your foot in the door.