1) Power of the case
Some people might think that the violin case is merely a vessel to carry the violin around. However the quality of the case can help sustain the life of the violin. Cases made in China may be sufficient for impact protection but the material used can produce fumes in hot weather which will gradually cause deterioration to the violin. A better quality case provides insulation against varying weather condition and provides better protection for the violin.
2) Rosin quality
Rosin is created from the resin of trees, typically pine; the resin is boiled and the fluid rosin is drained off. Good rosin is produced by purifying and reboiling: think of it as the equivalent of fortified wine.
General rule-of-thumb: the string should be suspended 4mm above the fingerboard (at the end towards the bridge. There are grooves in the violin body but apparently it's to create an antique look and doesn't affect the sound quality of the instrument. The bridge should be curved more sharply towards the E string.
- Do not leave the violin in the car boot. Try to keep the instrument in cool dry conditions.
- Before storing the violin, ensure that the bow hair is loosened (3-4 turns should do), and add a cloth between the string and the fingerboard to provide a buffer in case the bridge collapsed. It's good practice to wipe the rosin off the strings after playing to prevent deposits.
PS Feel free to give input on violin care and maintenance!