Diablocide

You need to think about your game.

When you think about your project, you can relate to the characters better and indentify inconsistencies in their relationships. You'll also be able to ponder your gameplay - maybe flesh out an idea you based your game around, or figure out a skillset for the monk character. This thinking can't just be "oh well think think think." It has to be focused, even if you're doing something else at the time. Wistful dreaming isn't going to get you anywhere in this regard. Choose a topic to paw over and focus on it.

But when do you do this thinking? Anytime you have a moment to yourself, really. I like to think about Demon Tower when I'm mowing the lawn. It gives me a good hour or two to play out interactions between characters in my mind or argue whether or not Goldurn should be in my party. Some other good times to think would be on the bus, before going to bed, while walking the dog, while eating breakfast. If you want to be serious about your project, pick a time to think and do it. Part of the design process is design, after all.

After you finish a thinking session, write stuff down. If you can write during that time, that's even better - jotting down a few skill ideas over a cup a coffee is great. When I'm mowing the lawn, however, I can't exactly take notes. If you focused your thought process, however, you should be able to recall the highlights of the mental planning.

Focus your thinking, find a time to think, and record the results. I think you'll be pleasantly surprised at how much that one dungeon's puzzle evolves when you think about the pros and cons of making it more complex.