The first 7 notes in musical alphabet to remember are A B C D E F G they are called natural notes A A # B C C# D D# E F F# G G#
Here is the whole musical alphabet from higher to lower sounds (from G down to Ab ) The G# and the Ab in the above lines are the same note because the musical alphabet starts over after G with one space between it and A
The other 5 notes are called sharps or flats and they fit between some of the first 7 notes.
Where they do not fit is between the B and C and between the E and F
so if we leave spaces for sharps or flats it would look like this A BC D EF G
the symbol for a sharp looks like this 
and the symbol for a flat looks like this 
and they both fit in the spaces we left between some of the natural notes.
When we add the sharps and flats to the natural notes it looks like this
A 
B C D E F G
The space with the sharp and flat is one note with two names.
Lets say if we were going from a lower sounding note A to a higher sounding note B the note in the middle would be A#
(A# sharp is one note higher than a A)
if we were going from a higher sound B to a lower sound A the note in the middle would be Bb
(Bb flat is one note lower than a B)
so A# sharp and Bb flat are the same note , what you call that note depends upon the direction of the sound. From a lower note to a higher note makes it a # sharp. From a higher note to a lower note makes it b flat.
Here is the whole musical alphabet starting from lower to higher sounds (from A up to G#)
Ab A Bb B C Db D Eb E F Gb G
Lets look at the alphabet leaving spaces for our sharps or flats
A BC D EF G A BC D EF G
Just remember there are no sharps or flats between B and C and E and F There is a sharp or flat between G and A
Lets apply this to the guitar now
our 5th string is called the A string, thats what note it makes when it is played open. The first fret on the 5th string would be A# or Bb the second fret would be a B the third fret a C the fourth fret a C# Db and so on up the neck to the 12th fret where it starts with A again.
The alphabet starts with the name of the open string, Lets look at the E strings. The 1st and 6th string are both E strings
This is where it is important to remember the names of the strings played open starting from the 6th string to the 1st string E A D G B E below are all the strings up to the 12th fret
Sorry I'll be back to add more soon. I'm just getting started with this page
Bruce A. Bowen