2 options I've used. No idea how much time you've got.

The first is to make cards with the fret number on one side, and the notes of that fret on each string on the other side... then learn a fret at a time. After a few days of repetition you'll have them all.

The second is to learn all the notes on the 5th (A) & 6th (E) strings, and then use the octaves to find the notes on the other strings. 2 strings higher and 2 frets higher, it's the same note but an octave up... remember you need to compensate for the tuning of the G string though, so you'd go up 3 frets.

EG:

12th fret of the high E string = E
9th fret of the G string = E
7th fret of the A string = E

or

12th fret of the B string = B
9th fret of the D string = B
7th fret of the low E string = B

You probably only need to learn 50% - learn the whole notes, and the sharps/flats fall into place anyway... My only other advice is that if this is for a test, probably only a very small number of the marks are given for this knowledge, so you may be better using your time elsewhere - play percentages.

Good Luck.... :)

**EDIT**

Forgot about the fretboard warrior game - download here - some of the guys I've taught found it useful...