We start with some basic information about tones and their arrangement.
There are 7 notes in the octave. Eighth note is the same as the first one but its frequency is doubled.
Its names are C, D, E, F, G, A, B in this precise order. I'm going to
use english name B instead of H, which is used in some parts of
Europe. B means H-flat here but not in this text, beware of
this.
Sharp/♯ (#) means tone raised by half-step and b/♭ means lowered tone. Example of this is C# (C-sharp) or Cb (C-flat).
Here comes the tricky part. There are 12 half-steps in the octave so the number of half-steps between the notes changes:
half-steps: 1 1 1 1 1 1 1 1 1 1 1 1 (all): C C# D D# E F F# G G# A A# B C notes: C D E F G A B C cumulated: 2 2 1 2 2 2 1
These cumulated steps represent major scale and therefore those 8 notes in the example represent C major scale.
You can pick any note in any octave and if you will follow these half-steps, you will get major scale for that note.
When you look at the guitar fretboard, each step is mentioned half-step (bass guitar illustrated, E is the thickest string of course, just like in tabs):
+------------------ open string tones | +---------------- headstock | | +----------- 1st fret | | | +- 3rd fret v v v v +----+----+----+ ...more frets G | G# | A | A# | D | D# | E | F | A | A# | B | C | E | F | F# | G |
There is tone C on the A string, 3rd fret. The C major scale can be played like this (tab):
C D E F G A B C G |-----------2-4-5 D |-----2-3-5------ A |-3-5------------ E |----------------
These are the positions on the fretboard:
G| . 2 . 4 5 G| . A . B C D| . 2 3 . 5 D| . E F . G A| . . 3 . 5 A| . . C . D E| . . . . . E| . . . . .
Since the fretboard is filled with half-steps, you can pick any starting position you want and play major scale, because these positions represent the major scale steps.
There are various minor scales. Major scale is the base and we make different alterations for each kind:
Natural 1 2 b3 4 5 b6 b7 8 Harmonic 1 2 b3 4 5 b6 7 8 Melodic 1 2 b3 4 5 6 7 8 Rock 1 2 b3 4 5 6 b7 8
Now we take the C major and make C natural minor, which means 3rd, 6th and 7th position flatted:
G| . A . B C | D| . E F . G | A| . . C . D | E| . . . . . | 3rd note is E, flatted is D# 6th note is A, flatted is G# 7th note is B, flatted is A#
When we fill in some surrounding notes we can see where D#, G# and A# are:
G| . A A# B C | D| . E F . G |G# A A| . . C . D |D# E E| . . . . . |
So now we know what natural minor is:
G| A# . C . D| F . G G# A| C . D D# E| . . . . G|-------------3-5- D|-------3-5-6----- A|-3-5-6----------- E|-----------------
Same applies here, if you follow this fingering you can play any natural minor scale.
Harmonic 1 2 b3 4 5 b6 7 8 G| . . . B C . D| . . F . G G# A| . . C . D D# E| . . . . . .
Melodic 1 2 b3 4 5 6 7 8 G| . A . B C . D| . . F . G . A| . . C . D D# E| . . . . . .
Rock 1 2 b3 4 5 6 b7 8 G| . A A# . C . D| . . F . G . A| . . C . D D# E| . . . . . .
Pentatonic scales have 5 tones per octave (major scale is heptatonic, which means 7 tones).
Major: 1 2 3 5 6 Minor: 1 b3 4 5 b7 (notes of major scale)
Applying these alterations we get:
Major:
G| . A . . . D| . E . . G A| . . C . D E| . . . . .
Minor:
G| . . A# . . . G| . . A# . . . D| . . F . G . D| D# . F . G . A| . . C . . D# A| . . C . . . E| . . . . . . E| . . . . . .
Some fretboard positions for major, minor and pentatonic scales (avoiding usage of open strings).
Half-steps: 2 2 1 2 2 2 1
| x . x x | x x . x | . x . x
Natural 1 2 b3 4 5 b6 b7 8 Harmonic 1 2 b3 4 5 b6 7 8 Melodic 1 2 b3 4 5 6 7 8 Rock 1 2 b3 4 5 6 b7 8
| x . x . | x . x x | x . x x
| . x x . | x . x x | x . x x
| x . x x . | . x . x . | . x . x x
| x x . x . | . x . x . | . x . x x
Major: 1 2 3 5 6 Minor: 1 b3 4 5 b7
| x . . . | x . . x | . x . x
| x . . . | . . x . . | x . x . | x . x . x | x . . x | . . x . .
The alterations of major scale for minor and pentatonic scales are from Rockbass ~ Beginner To Pro In Four Weeks.
For naming of notes in various parts of world see article on Wikipedia.