Hi FS.
There are two approaches to soloing: scales and chords.
To my mind and ear, soloing should be melodic, should tell a story. The best way I have found to achieve that end is to keep very careful track of the chords of the tune you're soloing to. The chords
are the tune in a very basic sense, and the strongest melody always has and always will consist of chord tones, those notes that make up the chords as they come and go.
Scales are the other way. They never, ever worked for me, so I can't say mch about them, how to use them, how to manipulate them. They always sound like scales to me; not only that, there is very rarely just one scale that will work over the whole tune, so you need to loook at several ... way too much for me to think about.
There are those, however, who actually see and hear scales to
be the solo. I hear this often in high speed shredding, where the player is simply playing scales up and down, or a certain mode. To me, this is not soloing, it's just playing scales. For those players, I guess my advice would be 'learn all the scale and modes'.
If you're into melody, then chords are the easiest, quickest way there. The trick is to see chords not as little localized clusters of notes, but as one long matrix of notes that stretch the length of the fretboard. That, of course, takes time, but once you can do that, you can literally see the infinite melodic possiblities waiting to be realized. Chords automatically sift away non-essential notes and highlight what I call 'boss notes' ... the good strong notes. Chord tones.
My book
PlaneTalk describes a very simple succinct way of seeing the fretboard as a whole, so if you feel you're ready for that stage, check it out at
http://www.thatllteachyou.com