Things to do when you find an abandoned kitten

Age
If you have rescued an abandoned or orphaned kitten, first of all you may need to find out its age so that you can provide it with the most appropriate care. Like most animals, kittens are born blind. The eyes begin to open in about a week. In 10 days, the eyes should be fully open. All kittens are born with blue eyes, and this colour gradually changes as they mature. The eyes will usually settle at about 7 weeks of age. If the orphaned kitten still has blue eyes, it is probably younger than that.
Another way to find out the kitten’s age is checking its teeth. According to the Cornell Book of Cats, the center incisors begin to erupt from the gums at about 2-3 weeks of age, the outer incisors at 3-4 weeks, the canines at 3-4 weeks, the upper molars at 8 weeks, and the lower molars at 4-5 weeks.
Bedding
In their first weeks of life, kittens need a warm, soft place to sleep that should also be free of draughts and dangers such as other animals and small children. The air temperature should be 85 to 90 F (29-32 C) for the first week of life, 80 F (27 C) the next three-four weeks, and 70-75 F (21-24 C) at six weeks. The higher temperatures during the first weeks can be maintained with heating pads, light bulbs, heat lamps, or hot water bottles wrapped in a towel. Make sure you don’t overheat the kitten when it is too young to move away from the heat source.
A tall-sided cardboard box makes a safe nest and keeps the kitten inside until it is several weeks old. Besides, the kitten will feel more comfortable in a small, warm area similar to one its mother would create. Bedding can be made of clean paper, cloth or towel. Line the bottom of the box with it and change the bedding daily, as the kitten will have accidents.
Feeding
If the kitten is tiny and doesn't have its eyes open, you will need to feed it kitten formula. You can buy it at any vet's office, pet store, farm and feed stores. If the kitten has its eyes open, is walking correctly and seems to be frisky and playful, then you are probably dealing with a kitten who is old enough to eat some solid catfood (usually it’s at about 3-4 weeks of age). Start out with some canned catfood and see how well it can eat that before moving on to the dry kinds. Some dry cat food manufacturers recommend soaking dry cat food in water to make it soft for the kittens, but a research shows it's not a good idea because most dry cat food is contaminated with bacteria and fungi spores; when you wet it, you bring all those to life allowing them to grow very quickly. Remember that even if the kitten is eating some solids, it will still need to have its kitten formula until around 6-8 weeks of age.

Photo by Matt Barnett

To feed the kitten, you can use a medicine dropper or even a kitten baby bottle. Many people think the bottle is best. Make sure you warm the kitten formula before giving it to the kitten. Remember that kittens love to caress (knead) their mother when they are nursing from her, so be prepared for this action. To protect your hands from the tiny sharp claws, you may want to use a warm towel.
Newborn kittens should be fed 6-8 times a day. By 2-3 weeks of age, the frequency should be gradually reduced to 3-4 meals a day.

If you're not sure how much to feed the kitten, consider its daily caloric requirements:

1st and 2nd wk of age: 6 calories per ounce of body weight daily
3rd and 4th wk of age: 8 calories per ounce of body weight daily

Please ensure fresh water is available at all times.
After feeding
After feeding, wipe the kitten's body with a damp cloth using short strokes like the mother cat would do. This will comfort the kitten, as well as teach it to eventually clean itself. The kittens should also be helped to urinate and defecate after each feeding. This is usually achieved by gentle stroking the genital area with a cottonball or tissue moistened with warm water. It stimulates the digestive system so that the kitten can go to the bathroom. In fact your kitten may want to go to the bathroom right then, so be on the lookout or set the kitten in a litter box. Generally, the kitten should be ready to try the litter box at about 4 weeks of age. Many abandoned kittens, however, will require extra effort and time to develop this habit properly.
Health concerns
Any kitten you have found without a mother and rescued should be taken to a veterinarian as soon as possible. The vet will check it for dehydration, worms, and other health problems that would require extra care. You can also schedule follow-up appointments for routine medications and shots.
Remember that, even if the kitten looks healthy (which is absolutely great of course), it doesn't mean it has no health issues. For example, cats with worms may have a multitude of symptoms (vomiting, diarrhea, weight loss or a dry and dull coat) or none at all. Sometimes worms may be observed in the vomit or in the feces, but this is not necessarily.
Another important thing to remember: whenever the kittens meow constantly without an obvious reason, it may be a sign that something is wrong, so take the baby to a vet as soon as possible.
Last but not least, if you bring an abandoned kitten into your home, keep it away from your own pets until you are certain it is healthy.
Things to do if you can't take the kitten to a vet
Ideally, you should always take a kitten you've rescued to a veterinarian to make sure it's healthy (and therefore it's not potentially dangerous to your family members and pets), and to provide the baby with all necessary treatment in time if there's an issue. However, if you cannot take it to a vet, remember about the following:

Keep the kitten away from your own pets for at least two weeks. This is called a quarantine.
Stray animals will usually have worms and fleas, so de-worming and anti-flea procedures can be necessary.
If you can't take the kitten to a vet because you have no time, try to find someone who will agree to do it instead of you.
If you cannot afford a vet bill, try to look for an animal welfare organization that can help out with vet bills, either with low-cost care, loans, or grants.

See also: Kitten health issues, part 1 and Kitten health issues, part 2

Things to do when you find an abandoned kitten

Why do cats have rough tongues?