Also, before I found that; I first learned where every instance of the half step pair BC were located. Once I could find BC everywhere I simply expanded it to A and D which are a whole step above and below every BC pair. Visualize like this A - B C - D; Final step is to do the same with EF learn where all the half step EF groups are and then eventually add the D and G a whole step above and below each EF pair.
There are also a number of phone apps (I like Fretboard learn) but there are many. These are great for when you are away from the Guitar, or waiting in a line or something.
A final tip, I found it helpful to say and/or sing the note you are playing. When you hit a G, say or sing G, it helps to drive the note into your memory with visual, physical, verbal and musical repetition.
These methods have helped me, but I am sure the Guitar Instructors here have some much better insight.
Good Luck to you!
TAT