Obtaining good tone on your violin is one of the greatest challenges, but within the grasp of anyone who has the courage to develop it. My recommendation is to
1. Listen to someone who excels on the instrument, and set a goal to become like them
2. Get an instrument that has good tone already. Sometimes this is half the battle.
3. Do a lot of bow workouts: Long bows on open strings, then adding your long bows to major scales/your chromatic scale.
4. Relax your bowing arm/wrist and rest your bow on the strings, then add pressure as you continue bowing back and forth(another bow exercise).
5. Don't over rosin!
6. Don't over tighten your bow.
7. Don't bow to fast. It is a good habit to learn to bow slowly. Try doing a 1 minute bow (one bow length on any string) and play a complete song on one bow (doesn't matter if it sounds good or not
8. Play with confidence. The violin is a sensitive instrument, but shouldn't be played timidly, even if you are trying to obtain a soft sound. Take charge of your instrument, and make it do what you want it to do. It is there to serve you!
9. Don't let your bow get down to close to your fingerboard, or up to close to your bridge.
Spend a lot of time playing, and not just doing exercises, but playing tunes/pieces as well. Be your own critic, and don't stop till you get what you want, and then keep on getting better than you thought you could ever be! -Brendan Booher