The fingers of the left hand should be slightly arched. You must be able to spread the fingers across the first four frets, using the fingertips only to hold down the string, just behind the fretwire.
The thumb must be behind the neck at all times and never reach over the top of the neck. It should be at a slight angle and approximately in line with the second finger of your left hand.
The right hand fingers should be slightly curved and positioned as close as possible to the first three strings. The wrist should be slightly arched with a slight twist downwards (see photo).
The right hand thumb should make contact with the bass strings slightly further along the strings than the fingers. The photo shows the correct angle for the thumb in relation to the strings.
The left hand fingers are numbered as shown in this diagram:
The letters p , i , m and a are used to indicate the right hand fingers.
p (pulgar) - thumb
i (indicio) - index finger
m (medio) - middle finger
a (anular) - ring finger