Hand and Wrist Vibrato

Start out with your fingers nice and erect in the correct position. Place the majority of the weight on the left
side of your fingers and pull back slowly with your hand and or wrist. Do this slowly until you feel the movement as a natural and comfortable one. After a while pick up the speed and imagine having a salt shaker in your hand trying to put salt on your violin.
Use hand and wrist vibrato for smaller vibratos than the one that you get using the arm. It is just as important to vary vibrato as it is dynamics. Learn as many different types of vibrato as possible to be able to express yourself appropriately to the music. Traditionally, high passages and classical music call for smaller, tighter vibrato whereas low and romantic music generally require wider, bigger vibrato.
Strive to make your violin as expressive as possible.