You may not have considered the possibility of keeping a chicken as a pet, but they can make wonderful additions to your family. If you live on an acreage there is probably no problem with keeping a pet chicken but if you live in a city, or sub-division, you will need to check your local by-laws regarding ownership of livestock. Some cities allow chickens as pets, others do not. If your city does allow chickens, find out if they have any restrictions regarding numbers, or other restrictions. They very likely will not allow roosters because of the loud crowing.
Chickens can live for many years, although often slaughtered young when egg production declines, you should plan on a pet chicken living for ten years.
One of the advantages to owning chickens as pets is that every day or two they will provide you with an egg. They usually go through a moult in the fall, they shed their feathers and regrow new ones, and afterwards slow down their laying process for the winter. Age and breed will determine how many eggs you get. A hen will lay eggs even when no rooster is present, however these eggs will not hatch.

Selecting a Pet Chicken
Female chickens are called hens, these are usually the best pets. Bantam, or Banty, chickens are smaller sized birds, they are often kept as pets because of the smaller space requirements. I would suggest getting two or more birds rather than just one.
Although you can buy fertile eggs and hatch them yourself, this is not always a successful venture. I would not suggest buying chicks under a few weeks of age, although,you can purchase young birds from a commercial hatchery. The problem with buying young chicks is generally they wont be sexed so you may get a rooster or two. Some commercial hatcheries will sell adult birds, particularly later in the season. If you are a first time owner you might be better off buying adult birds. A livestock feed store will have information regarding commercial hatcheries or you may find them on-line. In some places you can purchase birds at livestock auctions. Phone your local auction marts or ask at livestock supply stores if they know of any bird auctions. Many areas have specialty bird auctions several times a year.
If you are selecting adult birds, pick birds who are bright and alert, preferably of similar size and age. Ideally buy your birds from the same seller.
Another good place to buy chickens from is a petting zoo. Many will have surplus birds for sale. The advantage is that these birds will have been handled extensively and will be more friendly. You might even find chickens for adoption at your local SPCA or Animal shelter.
The breed is important as some breeds are more friendly than others. Leghorns, for example are not known to be friendly. Silkies are probably one of the favorites for pets because of their fluffy appearance, and they often like to be held. Araucanas are very interesting because they lay blue eggs. As some breeds are more common in some areas you will want to research those available to you. Decide what traits are important to you, size, color, egg laying, or friendliness.
Housing and Care
Your chickens will need a safe run and house. The house is where they will sleep at night and where they will lay their eggs in the day. It needs to have a place for them to roost, a wooden broom handle or branch will work well, They need a nest, which can be on the ground but is better if slightly raised. Three to four hens can share the same nest. The house will need a heat source in the winter if you plan on keeping them year round where temperatures drop below freezing. A protected light bulb will serve this purpose quite well. If you put cardboard on the floor of the hen house and lightly cover the cardboard with straw, then when its time to clean the hen house (twice a year is fine if your hen house is large and not over crowded) all you need to do is remove the straw and cardboard and you may not have to scrub the floor itself.
As with all animals they require fresh water. There are many watering systems available for birds from your local livestock supply store. They can be fed chicken scratch or laying ration, with scratch offered as a treat. Chickens love chicken scratch, it can be a good way to befriend a shy chicken. They also love dandelions, tomatoes, strawberries, and especially bananas. You can offer them treats daily and they will often talk to you to encourage you to bring them more treats. Make sure anything offered is free of chemicals, in other words if you do not pick it from your garden, make sure you wash it.
They need a safe enclosure, one that keeps them safe from predators and stops them from wandering off. Make sure they have a roosting place in the house as well as one out in their run, or yard. You will want to check once or twice a day for eggs, usually around noon and later in the afternoon.
Other Information
If you have never had chickens before you will be amazed at how personable they really are. You can not walk by without them softly clucking, calling you over to give them some dandelions. We have a garden and offer our pet chickens fruits and vegetables, which they enjoy. They also eat bugs, so do not use pesticides.
Tame chickens are easy to catch but if you must catch a nervous one, the best time is at night when they are a sleep and easy to sneak up on. Or have somebody help you to corner it. Most chickens are not mean however you may find some roosters are very aggressive and either demand food or act to protect their space, other than noise concerns, this is why I have not suggested you get a rooster.
I have not covered diseases because you could literally be living anywhere in the world and disease threats are different in different areas, very likely you will get the needed information at the time of purchase or from a vet in your area. Your birds will be healthiest if not kept over crowded.
Have fun with your new and unusual pet!