If you have ended up with a kitten that has no mother but still needs its mother to care for it, then the best thing you can do is find someone with a mother that has a litter and have that mother cat take in yours as its own. You can generally sneak the kitten into their litter by rubbing it against their own kittens and then leaving it with her. If you can't find a foster mother for the kitten, then you may need to care for it yourself. Here is a short guide to caring for an orphaned kitten.
Feeding the kitten – You will need to feed the kitten a good supplement that gives it the same type of nutrients it would be getting from its mother. This means purchasing kitten formula which you can get many places, with some of them being many grocery stores, a vet's office, a feed store, or a pet supply store. You will also need a kitten bottle. Warm the formula how you would for a human baby, making sure it isn't too hot.
When you feed the kitten, make sure you do so while it is on its stomach, not by holding it on its back as you would feed a human baby. Feeding it while it is on its back can cause it to aspirate formula in its lungs which can cause pneumonia which will more than likely be fatal to the kitten. New kittens need to be fed about every two to three hours. You can start introducing them to mashed up wet food with a bit of formula mixed in when they are around five weeks of age. Don't worry about giving a kitten water while they are on formula; they will get the water they need through the formula.
Helping a kitten relieve themselves – The mother cats help the young kittens to go to the bathroom by licking them down there to stimulate them to release urine and feces. When there is no mother cat to do this, you need to do it for them. Each time you are finished feeding them, you want to take a warm cotton ball that is about as warm as the mother cat's tongue would be and gently rub the kitten's lower abdomen, working your way down slowly until you see they have gone. They may not go every time, but you want to try for at least a couple minutes.
Keeping the kitten warm – The mother cat and other kittens help to keep the kitten's body temperature up. Without the mother cat and the other kittens, you need to keep them warm. You can do this by turning a heating pad on low, covering it with a towel or small blanket, putting it in a box, and putting the kitten on top. Check often to make sure it isn't too hot or cold.
Bring the kitten to the vet – Make sure you have the kitten checked out by the vet and ask them any questions you have. Also, be sure to return with the kitten when the vet wants it back to get it started on its pet vaccinations. You may need to bring the kitten in three times for it to be fully vaccinated.