What's the first thing you to do before starting a new DIY project?
If I'm building something from scratch, I first try to picture it in my mind or draw/model it to see what it's really going to take to accomplish it.
If I'm fixing something that broke, first I have a little crying session and then I think about all the steps needed to fix it. This helps me evaluate how long it might take and helps me determine when I should attempt the fix.