On solo's:
A good way of blagging a solo is to use the relative minor to whatever key the song is in, most people know the minor scale/Pentatonic shapes at least.
As example; if the song is in C major you could play in A minor/Pentatonic (the notes are the same) but obviously the emphasis/phrasing is on the C, E and G notes (C major triad).
Its a bad habit to get stuck in box shapes but i think we all do it, a good way to break free is to use linear movement on one string, its one of Malmsteen's favourates.
Another mistake is concentrating too much on speed, some guitarists can rip through lots of scales but they dont have any 'soul', the phrasing just is'nt there. Its worth listening to someone like Billy Gibbons in ZZ Top, he is sparing with notes but his solo's are very rhythmic and melodic.
On chords;
I try to color chords, i learnt from players like Johnny Marr, Pete Townsend and Andy Summers that you can make basic chords much more interesting by adding different notes. Without even knowing theory its easy to do and create an whole new different mood. There is also 'Chord Substitution', something Marr did in The Smiths was replace chords with similar chords like change C major for A min7 which is the same notes plus an A.
Hope some of that helps.
