Pencildragon's method is pretty much my method (look for anything to inspire an idea, write it down in music notation if you can, improvise on a common theme in multiple ways to end up with multiple tunes, choose one & build on that).
The thing is everyone has a different method or, if following similar methods to others, will have their own additions to such steps. The thing to remember is that it's similar to note-taking; all you're doing is collecting the ideas of others in order to form your own ideas. The problem comes in trying to convey those ideas in a way that others will understand (& this applies to all art forms, from music to literature & painting).
Personally, I use MuseScore to write down my thoughts into notation, or I do it by hand on paper. Other times, I just go straight into FamiTracker itself & create a theme (or revert to themes that I previously created or transcribed). If I'm stuck on trying to get something put together, I start a collaboration thread to see if anyone can give a possible idea to overcome a mental block (a good method to start a collaboration thread would be to make an FTM file with multiple tracks, where the first few tracks are the themes you've drawn inspiration from & the last track is what you can possibly muster from all your sources). Never underestimate the ideas of others & what they can possibly come up with, in spite of what little you may have created, because you can still build from the ideas of others.
General discussion about tracking, help and support.