Practice. That's pretty much it. Don't just practice alone though - try to get jam sessions with other musicians (guitarists, pianists, etc...). As far as note choice, if you're stuck on just the blues scale, for example, and you can play the blues scale all across the neck (from the 1st fret to the 24th, or 22nd), then try learning how to incorporate the major scale so that you can transition between the blues scale and the major scale seemlessly. Try doing the same with the natural minor, harmonic minor, etc... scales.
Hope that helps.


David
-G101