There are a handful of common routine maintenance practices for string players. Most of these can be handled at home or in the studio.
String replacement - Strings do not last indefinitely. They wear out, usually before they break. Most strings should be replaced at about a year’s time. Do not replace them with the cheapest brand (Red Label). They are cheap for a reason. Such strings will prevent your child from sounding their best, which is frustrating for us all.
The bridge - As we repeatedly tune, the bridge often begins to tilt and on occasion needs to be corrected. It is also common for it to be knocked out of alignment to the side, especially with younger players. Your teacher should keep an eye out for these and make adjustments when needed.
Pegs - Sometimes they slip, sometimes they stick. There are professional products and home-remedies to fix both of these. There are instances when the cause is poor fitting pegs, which needs to be fixed by a professional.
Bow rehair - This is the only one that requires a trip to the shop verbatim. Like strings, the hairs of the bow wear out from use, and need to be replaced. For the average student, this is also around a year’s time. I recommend alternating strings and bow rehair, so that every six months there is something new between them.
Any other issues that arise are likely beyond the scope of a home fix and should be taken in to a trusted shop for repair.
For recommendations on strings, rosin, cleaning agents, etc., view the resources page.