Breast milk can be kept in the fridge - keep it at the back of the fridge not in the door. When you come to feed baby, you might wanna warm it up as baby will be used to warm milk, just the way it comes out from you.
Don't microwave - the best way I find is to put some boiling water in a jug and sit the bottle in that for a short while - test the temp by dropping a little from the teat onto the inside of your wrist.....if you can't feel the milk its just right.
With formula, boil the water and add to the bottles ready (use water that is only boiled once), leave the bottles on the side to cool down (with tops on)....it is prob best to do this in the morning, and you can do enough to have your bottles for the next 24hours, when you need to feed babba add the formula, some babies will take at room temp, if not warm it up a little....change the water if the bottles haven't been used after 24hours.