Watch the Me Solo online guitar lesson by Jeff Scheetz from Blues-Rock: Secret Sauce
One way to get started boosting your melodic IQ is by knowing what chords you are playing over. This way you can start out by outlining arpeggio shapes and find the right register to play them in.
Singing while you are soloing can be very helpful as well. But at the very least "think" like a singer to help you phrase and choose notes that are melodically suited to the chords you are playing over.