Depends on what type of music, but you should always now a few simple ones atleast.
I would say know all of the major and minor scales by heart at the least. Other then that, yes it depends on your kind of music.
Thats an awful lot of scales to memorize. I'm going to mix 'em up, for sure.
You don't memorize them. You learn the notes in the key, and then you perform the scale formula.

For example, the major scale is WWHWWWH, or 2 whole steps, a half step, 3 whole steps, then a half step. So, if you want the G major, you go G A B C D E F# (Because of the half step)

Then you apply that formula for all the major scales.
Where is the first halfstep in the example you applied? If the second is F#, the first one should be B# or something?

Anyway, does this mean I have to learn all the notes on the fretboard?

Edit: Done a little research now, and I came up with the teory that B and E can't be sharpened, and that is related to that I have to hold down the 4th fret when I'm tuning string B. Am I right?
Last edited by MortyKBG at Aug 16, 2006,
B & E can be sharpened but it depends what key you're in. If your're in C# Major then it's C# D# E# F# G# A# B# C#, if you're in F# Major then it's F# G# A# B C# D# E# F#.