Watch the Skip To My Intervals online guitar lesson by TrueFire from Rock Guitar Greatest Hits Vol. 2
Lesson Source: Jennifer Batten's Rock Sauce for Lead
The guitar is a graph with vertical and horizontal lines. Ultimately you want to sound musical. That's the bottom line. But it's fun to experiment with just playing shapes within the graph just to see how it sounds. Once you can visualize a scale pattern in a position, you can try grabbing any of the scale tones at random in any order, and see how it sounds. It's especially fun to experiment with odd tunings and shapes, because you're not as familiar with scales and arpeggios or chord shapes when the guitar is in an open tuning.