Watch the String & Note Names online guitar lesson by Rob Garland from Chord Navigator: CAGED Triads
Learning the notes on the neck will help you find and create chords, write songs, and also improve your improvisation skills. Once you are able to find the notes that are used to create chords, you'll have no problem finding your way around the neck and will be able to play all the chords you'll ever need.
You probably know the names of the strings - by using a shortcut such as chord bass-note roadmaps you can visually connect the notes on the neck. For example, look at a C major chord. The bass note 3rd fret on the A string is the root of the chord (C), so if you want to know what note the 5th fret A string is, it must be a whole step up from C, meaning it's a D note. Look for octave patterns, 2 frets over and down from the low E and A strings, and the note will be the same. Move up a fret when looking for your octave using the D or G strings.