Here’s another approach to visualizing the fretboard (some theory involved):
One Way to Learn the Notes on the Guitar Fretboard
I’m not sure that this is “The Best” way to learn this, but it is one of them. This is advanced knowledge and chances are some of your guitar heroes can’t do this. But if you want to be a “master”, you will need this.
The Best Way to Learn the Notes on the Guitar Fretboard