1) You should have a pretty good grasp on keys, understanding what chords come from what major scales and how they relate to each other.
Don't forget about minor keys and how the 3 minor scales will change the harmoney (natural, harmonic, and melodic)
2) you should have an understanding of how to construct chords of higher sinorities within the scale, know that the 5 chord becomes a dominant when the 7th is added, and that the 5 chord in minor will often have a flat 9 attached to it and sometimes a sharp 5.
3)know the entire fretboard, and always be able to know how the note your playing relates to the chord. Remember, there are 2 ways to construct a solo, play melodies using the scale that constructs the key of the song, are playing off the chord, the 2nd way will produce infinit results, becuase you will be thinking chord tones rather then scale patterns and will make for more colorful results and introduce you to chromaticsm.
4)always.......play from the heart, good luck!
