If you can read music, take a book, such as Wolffhart (I think that's spelled incorrectly) violin studies or something similar, select a piece of music each day, and play it in 5th position, open position, 2nd position, etc... Start off with pieces written in the key of C. When you feel comfortable with that key move on to the next one(preferably in the circle of 5ths). You will eventually get to know the notes on the fretboard and you will improve your music reading skills at the same time.