Watch the Shifting Key Centers online guitar lesson by Shane Theriot from Solo Mojo
While soloing, besides the basic blues changes and one chord vamps, sometimes you will encounter having to shift key centers. This forces you to change modes, scales, etc. The main thing is not to let the chords get in the way of your melody or whatever statement you are trying to convey on the instrument. Here's a simple 2 chord modal vamp to practice this with.