I've heard it said that if you can't sing it, you can't play it. And when it comes to improvisation, I think this is a true statement. By vocalizing the pitches you want to play - before you play them - you train your ears and fingers to work together. The more you practice scales - and the more you sing them while you play them - the better you'll get at soloing. Probably one of the coolest artists I've ever heard using this technique is John Pizzarelli. Check him out.