Post notices on local bulletin boards and let people you meet know that you're looking for a place to look after. You should like animals if you're getting into housesitting, since the majority of people will have pets for you to look after. Some may only need to be let out once in a while, while others require much more intensive care. When you meet with the owner of the house, make sure they show you all the routines, including pet care. Ask them to write everything down and ask about special tricks they have to keep an animal quiet, get it inside, etc.
Every house has a quirk in it somewhere.
Whether it's that the tv doesn't work unless the bathroom light is on or the front door has to be jiggled in a certain pattern to open, make sure they tell you. You should be shown around the house and yard and meet any pets that you will be looking after. Find out if you should sleep in any one room or on the couch. Most people let you choose, but some are very particular. Make sure they show you where the cleaning supplies are kept, since it's inevitable that you will spill something somewhere and need to clean it up.