Game Designer

The first thing is that you should know what game design is actually about. You can read the book "The Art of Game Design" by Jesse Schell. If you are really think that this is what you want to do then read on. Otherwise check out other fields in gaming such as art and programming.
Learn some basic coding, preferably in C+. Also get hold of a game development suite such as Game Maker, Unity or Cocos2D. I personally use Unity because of their great asset store and user community. Start making games on these platforms. They should be simple enough! Don't go off thinking that I have this great idea for a super game that will make millions and start off biting more off than you can chew. This kind of attitude would portray you as a quintessential amateur gamer.
Also start paying close attention to the mechanics of every game you play, whether it is on mobile, tablet, PC or console. Question everything that you come across - how is the combat system designed, why are the rewards structured as such, etc.
Also check out Gamasutra - Blogs for tips from the industry professionals. Another website is The Game Prodigy “Game Design Careers.