SHARPS AND FLATS:
In between most notes is the sharp of the lower note (#).
B and E, however, don't have sharps.
Also, an F sharp (F#) can also be written as a G flat (Gb).
The # or b sign is drawn before the stave note.
The stems can be up or down, (like a d or p), it is still the same note.

OCTAVES:
The note letters are the same on the biggest and smallest strings.
Every 8 letters the notes repeat. A B C D E F G - A B C D E F G - A B C ...
This is called an octave.
On the guitar an octave is 12 frets, and half way along the string.
DURATION:
If the notes have holes in as above,
the duration of the note is twice as long (minims),
or if they are joined together, (quavers),
the duration is twice as quick.
For a summary of more note lengths, click here.
Of course, many programs can help you learn this.
To help make it simple, you can download the Guitartab.co.uk Tab and Stave Fretboard Simulator
Click here to download the right handed guitar version.
Click here to download the left handed guitar version.
Many guitar books follow a method a few notes at a time.
You may have taught yourself a lot just by reading tab and chord shapes already.
It may be easier to focus on one string at a time on this page so it is less confusing.