First of all, a kitten should be taken away from his mother in time. Because at home kittens are taken from their mother at the age of 6 - 8 weeks, the kitten that you acquire should be more than 8 weeks old when leaves his mother.
If it was often petted (of cause, not taunted) a kitten easily gets accustomed to people and usually becomes affectionate and loving domestic animal. A kitten elder than 12 weeks that was deprived from human attention is better not to take at all, for it will always be afraid of people and will keep the distance.
At the age of 7 - 8 weeks kittens usually cut all their sharp milk-teeth (or ready to do this): 14 on the upper and 12 on the lower jaw, 26 altogether. Most kittens weigh 700 - 800 grams in this age.
It is important kittens are well fed: backbone and ribs don't jut out, no round pot-like sides. If their mother looks poorly the babies are most likely to be treated badly. They should be tidy, lick clean, strong, healthy, and neat and be interested in almost everything, including your behavior. Check if they don't have louses, ear tick and there are no any signs of diseases, for example, yellow spots of diarrhea under the tail.
There should be no any defects of walk, lameness, egesta from nose and eyes. White kitten that has both eyes blue should be test for deafness.
If you choose a kitten from entire litter, choose a friendly and active one, not the most aggressive (i.e. the one that conquers all his brothers and sisters in plays), though it shouldn't be shy. Don't take the smallest and browbeaten one, even if you feel very sorry for it. Such kittens very often suffer physical and emotional disorders. From the very birth they eat most poorly and have the weakest immunity to diseases. Owing to bad manners of their brothers and sisters they grow up too timid, or aggressive. If you want to check mind status of your future pet set him in room where there's no cats to disturb it and watch it run after the paper ball or a piece of rope. Then clap your hand loudly and talk to the kitten for 5-6 seconds. If it'll run away, hide and refuse to go out right after you'll begin to persuade it kindly, then it'll probably be difficult for it to live in the house full of noisy children. Then ask if the kitten was inoculated and was vaccinations were made, and get the kitten to veterinary.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).