I think you're getting too technical. Most musicians have a wicked awesome solo or whatever that you hear on the album, but when they play it live, it's changed up a bit each time. To write it yourself, you mostly just play. I don't think it's so much planning out what to play as much as it is just playing. If you like it, play it again. If not, play something else.

Then if you want to write it down, use tabs with typical formatting so everyone else can read them.

If you want to practice, I use JamStudio.com. You can make a song with your own chord progression and instrumentation, loop it, and play along with. Check it out.

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- the highjumper
http://www.jamstudio.com