Watch the Using Variation in Leads online guitar lesson by Jason Loughlin from 1-2-3 Country
Composition devices are key to developing a solo in an organic way. Look what Beethoven was able to accomplish in his fifth symphony with just two notes. To me, this is the height of great improvisation. The four devices I most commonly use are repetition, retrograde, octave displacement and articulation. Repetition can be applied to a whole lick or just a piece of a lick. Retrograde means to play a melody backwards. Don't stress about it being note for note, any approximation will do the trick. Octave displacement is my favorite one. Try putting a lick in a different octave. Try taking just a few notes of a lick and put them up or down an octave. Articulation is one we all take for granted. I'm referring to slides, hammer ons, pull offs and bends. If there's a lick you normally bend try sliding. If there is a note you usually pick then try bending into it instead. Most players never put the ideas they already know through the paces, trying every variation. There is so much music in the simplest ideas. Your solos will be more cohesive as a result.