WHAT TO DO IF YOU FIND AN ORPHANED KITTEN OR PUPPY
If you find an orphaned kitten or puppy and have determined that it needs to be rescued (see my post "AAHHH!! A KITTEN!! DO I TAKE IT HOME?!"), there are a few very important things to do.
Warm the baby up. First, unless you live in the tropics, you baby is probably cold. Chilling (and also overheating!) can be lethal to little guys, as they are ectothermic and need an external heat source in order to function (they do not regulate their own body heat, a lot like reptiles). Wrap the little one up and keep it in your shirt or jacket until you can properly warm it (slowly!) on a warm water bottle or heating pad. Never attempt to feed a cold kitten or puppy! Babies cannot digest when they or the food they eat is cold, and the meal will rot in the stomach and possibly kill the tiny bugger!
If, instead, the baby seems to be overheating (ie found lying on a burning sidewalk in the summer), cool it down slowly by wetting and even blowing on its paws, nose, ears, and belly. Do not then let it cool too much.
Go to a vet, not home. Only a veterinarian will have the knowledge and tools to assess the baby's health and needs. Find a vet!
Absolutely no access to a vet? Prepare a nest box for the baby using a small, clean cardboard box (thank you, soda companies, for inventing the 6-bottle carrying box! It was made for nesting babies). Put a warm, not hot, water bottle/heating pad/something else you can reheat easily in the bottom of the box, with a clean blankie over it (I reclaim old towels, sheets and fuzzy blankets and cut them in to squares. Anything soft will work.) Make sure there are no corners that a baby can crawl in to--they have the tendency to crawl in to small spaces head-down and get stuck there. Also make sure there is a variety of temperatures available in the box by doubling the fabric on one side, but never leave more than a few inches un-heated. A tiny baby who crawls off the heating pad in to an unheated space can cool and die very quickly. Put something heavy (I use a piece of plywood) over the top to keep the baby in and cold/diseases out. You can poke a few holes in the box for ventilation. Keep the box somewhere quiet and warm, where other pets and people won't bother the tiny poopies inside. Even a closet will work, if you have no other options.
Get kitten/puppy formula. Baby formula and milk won't keep a nursing kitten or puppy alive. Get a formula made specifically for kittens or puppies (depending on who you have) and follow the instructions on the container. Dehydration is a major issue in rescue--most babies who have been on their own for more that a few hours will suffer from it, and it's essential that you get fluids in them ASAP. No way to get special formula? There are a few recipes here that are good temporary solutions (click image below):
No idea how old your kitten is? Click here to get some idea.
Now...get to the vet! And look through the TPR posts for more in-depth instruction, under the categories "rescue" and "you".