How to design and manage bigger personal projects?

"Hey /dpt/

I'm working on something more complex than I usually do. I wrote the "architecture" on a piece of paper and what I thought my program should use, is this one good way to do it? Or are there any proven "methods" to sketch the basis of your program?"

http://boards.4chan.org/g/thread/59235789#p59239204

I saw this question on /g/, and was wondering what you HNers do if you're planning for a large personal project (spanning a few months, say).