Understanding intervals is the key to unlock the chains on your guitar fretboard, enabling you to stop playing up and down scale positions and begin to think about note selection and what you want to "say" with licks you compose. With that in mind, there's one interval which I believe is the most crucial to utilize.
Related Lessons
Intervals in music are an essential foundation for understanding how to use various modal scales to your advantage.
While the best method is to actually combine these four approaches, visualizing the fretboard is something any guitar player would do well to work on.
The Circle of Fifths will help you understand and remember the notes in any key.