Well I think it depends partly on what style and what sound you're going for. But if you're a complete beginner, I can give you a few tips on how to start off which are universal.
1) Familiarize yourself with the scales you will be utilizing (be it pentatonic, minor, blues, etc.)
2) Practice that scale to death until you can play it backwards and forwards in your sleep. Practice with a metronome and with no distortion.
4) Get good at switching between solo boxes seamlessly.
3) Work on your "arsenal" of licks and riffs. Master the hammer-on, pull-off, and slide.
4) And lastly, develop a sense of "musical good taste", that is, being able to improvise in a creative and hopefully melodic way. It's not that long a road to reach that point, and the journey is fun as hell.