How to maintain a violin bow

Basics
Remember not to tighten the hair too much while playing, and loose it after playing. This can help the stick keep up it's camber longer
Over time some bows will develop a bend: to the right (looking down the shaft from the frog end) on the violin and viola and to the left on the cello and bass. This will result in bowing difficulties, unexpected noises and scratches while playing and difficulty in controlling the bow. A stick can be straightened, find a luthier to help you, also he/she can help you restore the camber in some cases. 
Rosin
The purpose of rosin is to help the bow in grabbing the strings. You want enough rosin to do this, but not so much that the excess creates a coating on the instrument or bow. Violin, Viola and Cello rosin are very similar, you apply rosin in long, slow strokes back and forth along the full length of the bow; Bass rosin is notable for being much softer - the better to help the bow grab the thicker strings, the technique is fast strokes from frog to tip — one way only. There are many varieties of rosin available; lighter rosin will typically grab less than darker rosin. When heat and/or humidity is high you may want to use a lighter rosin; when it is cold or dry, use a darker rosin.
You should rosin as often as you need to, which can mean a couple times a day or every a couple of days depending on your duration of playing, the type of rosin you're using and the surrounding weather conditions. This is something musicians develop a feel and preference for over time. In the early stages, consult your teacher for guidance.
Clean the hair
There are several way to clean the hair, typically using denatured alcohol and sometimes using water. You can choose to use a small container and dip the hair into the denatured alcohol or you can just use a soft cloth and wipe the hair, or a combination of several methods. But never forget to keep the stick and frog away from alcohol or any reagent. Re-hair is not necessary over years if you clean it in the right way.
Temperature/Weather
Be sure not leave your case in direct sunlight, in a closed car during hot weather, next to a heater and so on. Also use desiccant while necessary.