Full tone without forcing
We need to know how to play with a full tone. However, we cannot simply press on the strings to get a bigger sound.
Let it ring
We have to let the instrument ring on its own when we play. We do not forcefully make the instrument to produce a big sound, but rather the violin sounds full because you are allowing it to resonate.
Make the string vibrate
We hardly play on the surface of the string if we want any sort of ringing tone. We play into the strings enough to make the string to vibrate. You can actually see the string vibrate, especially on lower strings, when you add enough weight and pull the string with your bow.
Feel the vibration travel
Once you can see and feel the string vibrate, next thing you want to do is to send that vibration to the rest of the instrument. When the string vibrates, it goes to the bridge, then the top panel of the violin, then through the side panels and sound post the vibration reaches the bottom panel of the violin. We have to make sure that the initial vibration of the strings are sent all the way to the bottom panel of the violin.
Don't choke the violin
We will choke our violin when we press too much with the bow. We need to let it breathe so it rings fully.
Feel the gravity and arm weight
Place your bow near the frog. Make a somewhat straight line from your elbow to the hand, and keep your elbow rather high.
Adjust the height of the violin
Gravity works straight down, so if you want to use the gravity to your advantage your bow has to be set on the strings a certain way. Gravity will pull the bow down away from you if your violin is held slanted towards the floor. When this happens the gravity is working against you, not for you. In other words, you are wasting power that you could be using to get a full tone, and instead you are fighting the gravity.
When you hold the violin level, it looks like the following image.
Now, compare that to the next photo where the strings are level.
There is not much difference between the two but it is good to know the fact that when you hold the violin itself level, the strings are not level. To maximize the benefit of the gravity, you don't want to place the strings slanted towards the floor. Again, you don't really feel the gravity working against you when you hold the violin level. It's just a piece of information you should keep on the back of your head when you think about how you should hold the violin.
Hold the bow with middle two fingers deep on the stick
You can feel the weight coming from your arm more easily when you keep the middle two fingers deep on the stick.
Adjust the height of the elbow
This varies with every individual, but I recommend not to drop the elbow too low. When your elbow drops, your elbow feels the gravity. Gravity works straight down, so you will feel that on your bow with the same angle as your elbow is feeling. The problem with this is that your tone tends to be choked when you add weight on the string straight down. You want to be feeling the weight working toward the strings somewhat diagonally.