Lots of basic things to practice as well as the good suggestions above, in headings below that I can expand on if you wish.
Son File (Filay), for very smooth bowing
Note Starts and stops, including the ideas of lift and release
Bow arm movement
Bow hold
Legato bow change
On string and off string bow strokes
Good Tone
Good projection
Production and control of Crescendo and Diminuendo, from bow stroke to bow stroke or within one bow, in various combinations
Building Resonance (Maximum sound from minimum effort)
Studying the relationships between bow speed, bow weight and contact point to vary your sound
Picturing a sound you would like to make and listening as you explore variables
Feeling emotionally connected to the sound as an extension of self not as a result of doing X Y Z (the mechanics)
and the list goes on ........
DP