First of all, remember that taking care of your violin is very important. You cannot skip wiping off the strings or be loosening the bow very much at all. Your violin is fairly delicate and does not tolerate much abuse. There are a few simple routines to follow that will keep your instrument in excellent health!
Violin Bow Maintenance – Tighten your Bow Properly
Most bows only require two or three full turns of the screw, which is the metal (usually) octagonal piece on the non-pointy end of the bow. Turning the screw makes the bow hair more or less taut.
To make sure the hair on the bow is at about the correct tautness, look at the space between the hair and the stick in the middle of the bow. The width of that space should be about the width of a standard pencil. The hair should not be much further from the stick than that. If it is, the bow is over tightened and this stresses where the hair is fastened on the bow, causing hair to fall out eventually.