Mozart Should Not Sound Like Brahms:
Essential to being a fine musician is the ability to produce sounds appropriate to different styles, emotions and composers. The works of Mozart are masterpieces which often benefit from a particular sense of ease and effortlessness. Think sun, bubbles, high energy, celebration, and operatic joy!

Bow Speed:
In general faster bow speeds often convey a lighter, sunnier, more classical quality, while slower bow speeds communicate tragedy, stubbornness, difficulty, and suffering. Faster bow strokes are also useful when intensity and energy are key.
Beginning downbows with the frog angled slightly away from the bridge will help speed the bow and also lighten the frog, avoiding the gritty quality produced by playing near the bridge. Likewise, maintaining the frog away will help the sound production at the tip, because the bow is lighter at the tip and needs the heavier sounding point. (Remember, frog away from the bridge = tip into the bridge.)
The mixed bowing exercises found in Ivan Galamian’s scale book are useful. Familiarize yourself with the different feelings of sticky, resistant, slow bows vs. quick, free, traveling bows. In particular, exercises that alternate quick full bows with very slow bows will be challenging and rewarding.

Special Strokes and Smaller Muscles:
The flexibility of the wrist and fingers is vital to the lighter quality we associate with Mozart. The “Mozart” bowing, 2 slurred and 2 separate done in middle of bow, is used throughout the repertoire.

Phrasing:
Always know where you are in the structure of each movement.
Microphrasing at all times is recommended. Be clear about where you are aiming; show high points with both bow and vibrato.
Often crescendos in Mozart are best done by adding bow speed rather than arm weight.
Natural phrasing, up and down with the line just as you do in Bach, will give an organic quality to your playing.
Be aware of sequences; start them at a lesser dynamic and build them so that they make a larger line.

Vibrato:
Vibrato which is faster and narrower will work best with your lighter bow, but take care it does not become tense or constricted. Sculpt the rise and fall of harmonic tension in your line with your vibrato.