One of the most essential things in violin playing is to feel comfortable while playing. Standing with your arms lifted like a violinist is very demanding on the muscles and joints, and it is therefore essential to minimize tension.
The most essential thing to achieve this is a good posture. Students should be encouraged to play in front of a mirror and have a friend or parent look at them from behind. Common problems are raised shoulders, twisted or curved spine and craning of the neck and head. To help prevent this, the right choise of chin and shoulder rest is essential. Persuade the music shop to let you try a wide range of chin rests and if possible have your teacher come with you to help you choose. The fixed shoulder rests in common use are very good for orchestral playing. However, for a beginner I recommend using sponges and cushions which are cheap and adjustable. Buy a large quantity and experiment (cutting and gluing) before you invest in the more expensive Wolf shoulder rest or similar.
Once a good setup is found, a good basic posture for both sitting and standing should be worked on. Your teacher will be able to help you out with this. The spine should be in a good upright position and your shoulders should hang on the spine in the most natural way possible. Swaying at the hips as well as hunching your back and shoulders is common among all players, and are things to look out for. When sitting you should be able to feel grounded. Avoid crossing your legs or feet but plant both firmly in the ground slightly parted and keep the torso in an upright position.
Do not be afraid to move while playing. This eases tension. However, try to move in a way that is productive for your playing. On an upbow move the violin towards the frog and vise versa. This can as everything be overdone but moving your violin in the same direction as the bow is moving is even worse for sound production.
When taking a break there are a range of stretches and shakes you can do. Yoga can be very helpful to release tension. I try to teach my students some of the various stetches I have learned over the years. Funny as it might sound, keeping fit is important for a violinist so sports are encouraged - though not all sports are equally good for a musician. Choose something where you are less likely to break fingers.
I hope this can help violinists on their journey to a more healthy relationship with the instrument. Please contact me if you have any questions or wish to have a lesson to get some advice.
Anne Marie