(Ie: index for 1, middle for 2, ring finger for 3, pinky for 4 & 5)
Make sure you have your grip correct too, a lot of people feel more comfortable with the Tom Delong way of playing by having your grip swallow the back of the neck - don't do it. Have your thumb placed in the middle and your hand cupping beneath the neck to allow your other digits to stretch.
Eventually you'll have good muscle memory and your hands will start to get a wider range of notation.
Sinestro Corps Member