When bottle feeding, allow the kitten to determine the speed of the feeding, otherwise you may drown the kitten by allowing the milk to back up into the lung area. Never force the pressure or speed of the milk flow. Purchase a good scale and weigh the kittens at birth and daily until they reach at least day 21. Make sure you weigh them at about the same time each day. If you see a kitten having problems, weigh more often.
Many breeders use heating pads to warm and keep kittens warm.
Most kitten die from being chilled too long. Purrinlot suggests not a dry heating pad but other warm solutions. A Heating pad works if it isn't one of dry heat. The dry heat will dehrydrate the kitten faster than anything and that can cause you to lose him as well. Pottying the kittens is necessary from time to time.