Planning software development [closed]

Question

I'm fairly new to programming (still a student), and I haven't had much experience with planning out my software development. Usually if it's a large project, the profs break it up into steps for me. If it's smaller, I usually just dive right in. This has worked so far, but I'd like a better process. I'm planning to do a rather ambitious project, and I'm worried that my code will turn out a mess and/or take a lot longer than if I had planned it properly. I'd like a method/technique/advice for planning out my software development.