To be honest. The best ideas come when you are not even trying hard at it. Like walking down the street, overhearing an argument, or my personal favourite - in the shower. But no matter what just keep a notebook.if that is too big, use the note pad on your phone. so that when even the smallest idea pops in your head (which you think is cool) write it down. It is not enough to just write it down either, don't stop mulling over it, for about an hour or so. (Because from a zen advice, if you go chasing your thoughts, you get too obsessed and lose opportunity for new and greater ones.) Consider a few things like possibility, implementation, improvement etc. After a while (say a day or two) read over your notes, if you still like the ideas, you just might have yourself a viable project.