Drawing the bow across the strings.

Learn to draw the bow across the strings with as smooth and even sound as possible. Your fingers should be very flexible such as the hair on a paintbrush. Spend extra time working on your bow changes at the frog of the bow since it is the heaviest and most sensitive place to play and change bow directions. Practice drawing the bow in front of a mirror. Make sure that you bend your elbow and not your shoulder. Practice very slowly no matter how ugly and painstaking. Spend most of your  allocated practice time on the difficult techniques.