GameMaker - http://www.yoyogames.com/make
Step One: Make a game (not just edit an existing one)
Step Two: Make the game fun
Most people don't get past Step One because completing a game is a task in and unto itself.
It's a fun way to play with game design and see how well you might be cut out for it.
Another free way is to simply create board games and see how that goes.
The best bet is to find a particular aspect of game design that you like - coding, art, 3D, world building, etc - and focus on that as you greatly improve both your chances to find an area you excel in and to find a job in the industry.