Guitar is a really cool instrument. We don't *have* to learn what notes we're playing. We can just play a few chord shapes and start impressing the ladies right away, unlike most other instruments. They all have to start off reading music and finding where notes are the first day of lessons. Guitarists can just go online and find their favorite tabs and never read a lick of actual music.
This is a blessing... and a curse! Guitarists tend to be better at playing by ear but horrible at reading music. The famous joke, "How do you get a guitarist to shut up?" is appropriately answered, "Put music in front of him." But knowing how to at least find notes on the guitar is very important.
Memorize the notes on these two strings. This is ALL you have to memorize. Trust me.
Notes on the E String
Notes on the A String
Any note that isn't listed above is a sharp or a flat. A sharp is a note one fret closer to the bridge from the "natural" or regular note, and a flat is one fret toward the nut. The 2nd fret on the E string is BOTH an F# and a Gb.
If you've ever played a piano, the notes listed above are all the white keys, and the sharps and flats are all the black keys.
What about B# or Cb? Or E# or Fb? You might have noticed on a piano that two sets of white keys have no black key between them. There's no associated sharp or flat between these. So a Cb is really the same thing as a B, and a E# is really the same thing as an F.
Memorizing the notes above is most of the work. Now, using octaves, we can find any other note on the guitar from those two strings! An octave just means playing the same note but higher or lower. For instance, you have two E strings, right? But they're not the same note - one is higher and one is low. Both are E, and they sound similar. These two strings are in different octaves but both E.
Octaves can be used to find notes. Here is a G with three other G's nearby:
Remember where the other notes are *in relation to* the first G. Then you can move this pattern around. The same pattern will follow you around the fretboard. Here's the same thing with a D:
This can be used in reverse! If you're trying to figure out what this is...
Just reverse the pattern all the way down to the E string, and it turns out to be an A. Here's the pattern of octaves starting on the A string. It's pretty similar:
So using those two patterns of octaves, you can find any note on the guitar. Remember that all notes repeat at the 12th fret - everything starts over.
You can also solo using octaves. If you pick two notes in the patterns above that are one string apart and block out the other strings, you'll get a sound sort of like a 12-string guitar. Then just move it all over to solo. This technique is used a lot in jazz but also in rock (the solo in "My Friends" by the Red Hot Chili Peppers comes to mind). Make sure you block out all the other strings when you play octaves!
Finally, use octaves to add some variety to boring power chord songs, especially when you want to play a melody or emphasize certain notes. Here's an example by the Juliana Theory: