The snare drum is the most complex instrument on a standard drum set, and fixing it first requires a diagnosis of which part of the drum needs repair. Each piece of the snare drum requires different approaches to fixing it.
Do not attempt this repair unless you are skilled with wood work since further damage could ruin the snare.
Check the snare throw mechanism. This is the most complex piece of the snare drum, and it is responsible for holding, raising, lowering and adjusting the tension of the snare wires. If the snare throw is not functioning properly, remove the screws that secure it to drum and inspect it carefully. If any part of the mechanism is bent or damaged, it will probably need to be replaced. Replacement throws are also easily available from most instrument shops. If the part does need to be replaced, it presents an excellent opportunity to upgrade to a high-quality throw that will improve the overall function of the drum.