I don’t think I would use memory techniques to memorize the fretboard, but other people here might have some other ideas about that.
I’d memorize the names of the notes of all the frets that have dots on them first. Some of them are easier than others, because they are the same as some of the open strings, like:
- 5th string, 5th fret is a D (the open 4th string is a D)
- 6th string, 5th fret is an A (the open 5th string is an A)
- 5th string, 7th fret is an E (the open 6th string is an E)
- 2nd string, 3rd fret is a D (the open 4th string is a D)
- etc.
Thinking about the relationships can help memorize them faster.
After being comfortable with those notes, I’d expand to this method:
- Choose a note from the circle of 5ths, like C or F. (That link has mnemonics for the circle of 5ths.)
- Find the lowest C note on the lowest-pitched string (the low E). By this point you would know that the 7th fret dot on the 6th string is a B, so you only have to go one fret higher to the 8th fret to find the C.
- Move to the 5th string (the A string) and find the lowest C there. It will be on the 3rd fret.
- Keep repeating on all the strings in order until you find the lowest C note on every string.
- Then go to the next note in the circle of 5ths (or backwards in 4ths). C → G → D → A → E → etc. and find the lowest notes on each string.
- You can mix it up between days by finding them in order from 6th string to 1st string or vice versa.
I would practice that once per day. If it’s slow at first, start with just one or two notes, like C and G. As those become faster, add more. Eventually you will be able to think “C” and your hands will know exactly where to find it on every string.
(If that doesn’t make sense, let me know and I could record a quick video example of the exercises.)
There are more ideas in the music-memorization section if you haven’t already see it.