Software Project - Recomendations

Hi.

I am near to start a big software project, I have worked with Autoit for 4 years and have done some great programs but I have never had like a structured way to do it, I just started to write the code and just that.
I am not a software engineer, in fact I study Business Administration, but writing software is my passion, and I want to improve the way I do it. So my question to you the Software Engineers (or software geniouses) is what recomendations can you give me to maintain a big project, I mean:

How to keep track of the code

What should I do first (core, UI, for parts...)

Which software do you use to do each thing...

How is your developing enviroment

Any suggestions.

I hope others like me, who didn't study software developing careers can learn here, the things that we should know.

Thanks!