Unless you are a shredder, I've always heard that a good way to come up with a solo is to whistle while playing the chord changes. A lot of the solos you remember from songs are simple ones that you can whistle. Maybe record yourself whistling and then try to reproduce the notes on guitar. I did this for one of my songs, and liked the whistling solo so much I just left it in the recording! Quick pitch changes are always interesting too. That's why just playing scales are so boring because you rarely play notes that are too far apart. If you play Blues type stuff, the "call-answer" is nice in solos. Play the same (or similar) small lick in two different octaves. Playing it in the lower octave would be the "call". Playing in the higher octave would be the "answer". -- Ravin