A challenge for almost all beginners is to learn the notes on the fretboard. The notes on a guitar are inherently more difficult to learn than on a piano, since you don’t have the help of white and black keys. But here’s what worked best for me:
1) Learn the notes on the low E string. Almost everyone learns this first. Knowing just the notes on low E you can power chord your way through a lot of songs :-).
2) Now you obviously also know the notes on high E (illustrated below as the same notes having the same colors).
3) Here’s something that was a bit of an eye-opener for me: the D string is exactly two frets shifted up the next from the E. This means third finger in a three-finger power chord is on the octave (same note) as the first finger.
4) So now you know three strings, from really only knowing one :-). Time to learn a new string – A.
5) The G string is two frets shifted up from the A, just like the relation between E and D.
6) Now there’s only one string left. Either you just memorize that two, or you use the fact that B is two frets shifted down from A. So just like the relation between E and D and A and G, but in the other direction.
So now you know the whole fretboard from really only memorizing two strings!
Another good exercise is to find and play all instances of a note across the fretboard. Start with all Es. Good luck!