The only really solid rule of feeding is to make sure you're not feeding your starter boiling hot water or overwhelming it with a vastly unequal amount of flour or water.
The only really solid rule of feeding is to make sure you're not feeding your starter boiling hot water or overwhelming it with a vastly unequal amount of flour or water. Lukewarm or cold is fine. Boiling is one of the few things that can actually kill your starter, so avoid that and you'll be set. If you keep the starter in the fridge, when you feed it, let it chill out on the counter for an hour or two with the lid off, then screw the lid on and put it back in the fridge.