First of all, I'm in the habit of writing songs or licks or whatever, that I can't play up to speed right away. Basically, should I stop doing this? What I usually do is write a rhythm part which I can play then play out a lead part slowly over it to make sure all the notes sound right, but it takes me a while to learn it at full speed. I feel like I'm cheating, if that's the word to use.

I'm wondering if theory is something I should start to pick up, I'm not really sure what it involves completely, but any suggestions on where to start would be appreciated.

When writing instrumental pieces I tend to either get too random in my parts or focus too much around the same idea, is there anything I can conciously do to stop this, or is it just something I'll have to deal with?

Thanks for any help.