Bow hold

This is the basic bow hold: rounded thumb and fingers, including pinky:

The thumb is opposite the second (middle) finger's lowest joint. This circle is the basis of the bow hold, the thumb a kind of 'see-saw' pivot.

At the heel:  The hand is more upright (supination).  The rounded pinky takes weight out of the bow.  The index finger does not pull inwards, as this would take the bow off its straight track.

At the tip: The arm reaches forward to keep the bow on track. The hand leans more into the bow (pronation).   The index and second (middle) finger lean add weight through this pronation.  

The pinky may let go of the bow if it can't reach easily.

The third finger (ring finger): relaxes over the bow, resting near the white dot on the bow frog.

Don't let the thumb and pinky get stiff - that's the number 1 problem people have when they can't produce a smooth tone or off-string bowings.




TONE PRODUCTION

Control the 3 elements of tone: Soundpoint, Bow Pressure and Bow Speed.  If one changes, another must also change e.g.: if you are at a soundpoint near the fingerboard and increase pressure, the tone will be flat and crushed.  You need to also either increase bow speed or change the soundpoint.

Remember: near the bridge soundpoints are 'elephant zone' - the bow needs to be slower and heavier. 
Nearer the fingerboard, it's the 'cheetah zone' - the bow needs to be faster and lighter.

These zones, though, all get closer to the bridge when playing on higher strings and higher positions.  So on the E string, the 'cheetah zone' is still a fair way from the fingerboard.

We all need to experiment with Soundpoind, Pressure and Bow Speed on our own violins to know how they respond.  Try various dynamics in each soundpoint.