The range of the average guitar fret board is 20 frets.  What you need to memorize is the names of the notes for each open string (they are at octaves on fret 12 and will have the same name at that location) and the names of the notes at fret 5 (these will be the same name as the next open string) and finally the note names on strings 5 and 6 from the open position up to fret 12...this is for chord root identification.

 

 

 

The 6-string guitar has three ranges using 2 strings per range.  We will call these ranges bass, alto and soprano for demonstration purposes.  The bass guitar has 2 ranges we will call bass and tenor.

The low range, or bass, is where the origination of all chord roots is generated.

Observing the low range chart to the right and noting the chart above for location on the TAB, you can see what the note names of specific frets are on the 5th and 6th strings.

Any fret not listed on the TAB are considered sharps(#) or flats(b).  On string 6 fret 2 is not listed in the TAB.  Fret 1 is F so fret 2 is F#, also fret 3 is G so that makes fret 2 also Gb.