i'll start with some scales. the ones that are the most common 
are major and minor. to play a major, play this pattern anywhere 
on the fretboard. this particular one is in D 

————————————————————
————————————4—6—7———
——————4—5—7—————————
——5—7———————————————

and to play minor, play this pattern anywhere on the fretboard. 
this is also in D

————————————————————
———————————————5—7——
—————————5—7—8——————
——5—7—8—————————————

scales are useful because when you play a song, it is in a certian 
key. so when somebody wants to play a song in D major, you would 
write a line using notes from the D major scale.

to help with knowing which position plays what note, a good thing 
to know is the musical alphabet. for example, on the A string, 
the notes will go as follows.

A A# B C C# D D# E F F# G G#

another thing to remember is that sharps(#) and flats(b) can 
be the same thing. for example, a A# is the same as a Bb.

a good fingering exercise to start out with is the 2 finger exercise. 
you will use 2 fingers and play this using only your first 2 fingers.
——5—6———————————————
——————5—6———————————
——————————5—6———————
——————————————5—6——— 
then play again, but reverse this time.

after you do that for a while, try with the first and third fingers, 
like this
——5—7——————————————————
——————5—7——————————————
——————————5—7——————————
——————————————5—7——————
and again, play back up the neck.

and finally you use your first and fourth fingers, like this
—5—8———————————————————
—————5—8———————————————
—————————5—8———————————
—————————————5—8———————
then play back in reverse. and you don't need to start at the 5th 
fret, play wherever's comfortable.