One healthy, friendly young rat, from someone who handles the rats daily.
Another healthy young rat, same or similar source, same gender as first.
Permission from landlord/parents/whoever might object to your new rodent buddies.
A large cage. See below for dimensions.
Healthy bedding. See below for specifications.
A water bottle to hold drinking water. Choose a gravity-feed type, 8-16 oz. with some kind of a hanger to hang it on the cage.
A food dish, large and heavy and difficult to tip over.
Rat food, such as lab blocks or a seed/grain mix designed for rats.
Daily small amounts of fruits and/or veggies for variety in the diet.
Toys such as boxes, tubes, etc. to sleep in, climb in, and play in.
Daily attention, love, and affection
Yield: One or more happy humans and sweet, happy, healthy rats. Joy enough for all to share.
First find the appropriate cage. This cage should ideally be metal (because it has better ventilation and gives the rats an opportunity to climb in the course of their play). The floor should allow the rats to walk directly on their litter/bedding to prevent irritation to their feet, though the ramps and ledges may be wire. Make sure any wire the rats walk on is 1/2" by 1/2" mesh or smaller to avoid having them trap and break their legs. Solid shelves and ramps are a big plus! Make sure the sides are not too "open"....that the holes in the sides of the cage are not big enough to let the rattie squeeze out. 1/2" by 1" or 1/2" by 2" openings will keep even baby rats inside the cage. If you cannot find a suitable metal cage, find the largest aquarium you can. NEVER use anything smaller than a 10-gallon (which should be used only temporarily for babies, not for adults) and definitely NEVER use a Habitrail, which is simply too small for a rat of any size.
Next, get the things your rattie will need:
Healthy bedding. DO NOT USE PINE OR CEDAR BEDDINGS. They are toxic and will damage the lungs and livers of your ratties. Choose instead aspen or a recycled paper or wheatgrass bedding. Examples are Gentle Touch, CareFRESH, BioFlush, Yesterday's News, Cat Country/Critter Country, LandM Aspen, Sani-Chips, etc.
Food dish/Water bottle. You want a food dish that is not easy to tip. Rats play with everything in their environment, being both creative and very intelligent. They will happily tip their dishes and scatter food hither and yon, making it less than sanitary, so I suggest a heavy food dish. By the same token, give them water in a bottle rather than a dish. If you put their water in a dish they will just use it to baptize their bedding and will look up at you pitifully and thirstily. So give in and get them a good sturdy water bottle and holder.
Food. A good base for a rattie diet is Lab Block. Most pet stores and feed stores either have this or can order it or tell you where to find it. It is a nutritionally complete if rather blah-tasting (or so my ratties say) staple diet. It's good to add a seed/grain mix once or twice a week and small amounts of fresh fruits and veggies at least several times a week for variety and added nutrition.
Toys. You need not break the bank on this one. Cardboard boxes and paper mailing tubes (or toilet paper/paper towel rolls for little babies) will be great toys. So are sections of PVC pipe from the hardware store. Also many toys are available in the small animal and bird sections of your pet shop. Change toys frequently to prevent boredom.
Finally, find and choose your ratties. Try the Humane Society, any local breeders, or a pet shop as a last resort. Look for healthy rats who do not sneeze or wheeze or have wet bottoms or red gunk around the noses or eyes. When you open the cage they should come and sniff your hands and want to play with you. They should not huddle in the bottom of the tank as if you were going to eat them. They should have shiny fur and clear eyes and look healthy. The males should be in a separate cage from the females; if not, you may be bringing home a pregnant girl. Also if any rat in the group is sick, don't buy from that place because illnesses in rats tend to spread around and the stress of going to a new home might be enough to make an apparently healthy rat show symptoms of an illness it is carrying. Contact a local rat club for the names of local breeders.
Note: You will get the best results by mixing a female rat with a female rat or a male rat with a male rat. A single rat is lonely and bored--please don't condemn a rattie to a solo existance. If you choose a male/female pair you will have a new litter of up to 20 babies every month!!!!!