Housing

When choosing an enclosure for your bunny, it needs to be 3 to 4 times as big as your bunny when it’s stretched out, and tall enough for your bunny to stand on its hind legs. Avoid enclosures that have a wire floor because bunnies have sensitive feet and the wire can be harmful. Same goes for litter boxes that have a wire grate - either choose a different one or remove the wire grate.
Your bunny will need lots of exercise! If your bunny is not free roam, consider a large X-pen with plenty of space for them to run, binky, and play.
Be sure to bunny-proof the room you allow your bunny to play and exercise in - bunnies love chewing cords and furniture, and have the tendency to dig up carpet. Place cord covers on accessible cords and wires, or hide them behind furniture. Provide a grass mat or a rug that you don’t mind your bunny digging at to avoid your bunny digging up the carpet. You can also make your bunny a dig box filled with shredded newspaper, phone books, or hay.
Provide your bunny with toys and other forms of enrichment and entertainment - this includes cardboard hidey houses, cardboard toilet paper rolls (with the paper stripped off), willow balls and sticks, and grass mats / huts, to name a few. Click here to read more.
Bunnies tend to do their business in one spot, usually a corner, whether it’s the corner of their enclosure or a corner of the room they are residing in. That being said, set up a litter box in their preferred corner complete with bunny-safe litter and hay - bunnies like to poop and snack at the same time.
Speaking of litter boxes, your bunny’s litter box should be cleaned daily and have the litter replaced.
Do not use cat litter or wood chip bedding as litter for your bunny - cat litter is made to “clump” when wet, and if your bunny ingests any of this kind of litter, it can cause serious digestive issues, and possibly death.
Bunny-safe litter consists of litter made from recycled newspaper, such as Yesterday’s News, Carefresh Paper “bedding,” or Kaytee Clean and Cozy paper “bedding.” The unscented variety is preferred.
Be sure that your bunny’s living space is sealed from drafts during cold weather, and provide a cool place for bunny to lay during hot weather, such as a piece of stone, ceramic, or marble tile. You can give your bunny a frozen water bottle to sit next to, or lightly spray its ears with cold water during hot weather.
Hot Weather Concerns
Cold Weather Concerns

Diet and Feeding

Hay and Pellets

Provide your bunny with an unlimited amount of hay! Hay is full of fiber, which keeps a bunny’s digestive system healthy. Timothy hay is preferred for bunnies that are 7 months and older, and Alfalfa hay is preferred for bunnies younger than 7 months. This is due to the fact that younger bunnies need more protein than older bunnies, and alfalfa hay is abundant in protein. Never let your bunny run out of hay - keep a hay trough attached to your bunny’s cage, and be sure that the hay has minimal dust, and zero insects or pests before giving it to your bunny.
¼ cup of fiber-rich pellets should be given to your adult bunny per 6 pounds of body weight. So, if your bunny weighs 3 pounds, you can give up to 1/8 cup of pellets a day, and if your bunny weighs 6 pounds, you can give up to ¼ cup of pellets a day.
Baby bunnies, however, should be provided with unlimited pellets until they reach 6-7 months of age. At 7 months, pellets should be decreased to ½ cup a day per 6 pounds of body weight.

Water

Bunnies should be provided with fresh, cool water every day. They will not drink warm water.
Be sure to clean your bunny’s water bowl or bottle frequently to prevent the build up of bacteria.

Veggies

Introduce fresh veggies to your baby bunny around 3 months of age - start slow as to let their digestive systems get used to it.
Adult bunnies should be provided with a minimum of 2 cups of fresh veggies a day.
Avoid iceberg lettuce - it has no nutritional value for a bunny and may cause digestive issues such as loose stools or diarrhea. Stick to dark, leafy green veggies.
Avoid veggies that are high in sugar, such as carrots, and restrict these to only be given as a treat.

Click here for a list of bunny-safe veggies, and veggies to avoid.

Fruits

Fruits should be given to your bunny as a treat considering the sugar content in most fruits is very high.
Click here for a list of bunny-safe fruits, plus fruits and other treats to avoid.
Although some treats at your local pet store may be labled for bunny consumption, such as yogurt drops, these are NOT SAFE OR HEALTHY for bunnies to eat.

Grooming

Do not, I repeat DO NOT bathe your bunny! Bunnies can develop hypothermia and go into shock when completely wet so please avoid this at all costs. If your bunny has dirty feet or a dirty bottom, you can take a slightly dampened washcloth to clean that area only, and then dry your bunny off as best as possible. If your bunny does not have a disability that prevents it from being able to effectively clean itself and this problem persists, chances are you need to clean the cage more often.
Brush your bunny 1-2 times a week to remove loose hair that can make your bunny uncomfortable - brush daily during periods of shedding, or if you have a bunny with long hair such as a Lionhead or Angora.
Bunnies go through a molt about twice a year, where they shed their old coat and grow a new one - prepare for lots of shedding and lots of brushing at these times.
Long-haired breeds of bunnies may need to have their hair trimmed. You can read more about that here, but NEVER trim a bunny’s whiskers. They are important sensory tools that help a bunny navigate the area around them.
Nails should be clipped every 1-2 months using a pair of cat claw clippers. Take care not to clip the “quick” or blood vessel that is contained within the nail or your bunny will begin to bleed profusely (have some styptic powder on hand in case this happens). The quick should be farily visible in bunnies with white nails, but not so much in bunnies with dark colored nails. If this is the case, use a flashlight to shine under the nail to locate the quick.
Bunnies have scent glands around their anus and on the bottom of their chin - they’re usually pretty good about cleaning these areas themselves but sometimes we have to help them out. The discharge resembles a waxy substance - to remove it, use a q-tip dampened with warm water and either hydrogen peroxide or mineral oil to remove the residue build up in these areas. You should check your bunny’s scent glands once a month to assess the need for cleaning.
Periodically check your bunny’s ears to make sure there isn’t a lot of wax build up, or even a mite infestation. To clean your bunny’s ears, take a cotton swab dampened with warm water and saline solution and swab around the inner ears. Do not stick the cotton swab too deep in the bunny’s ear canal or you may cause severe damage. Watch this video for more info on how to clean your bunny’s ears.

When it comes to grooming or regular health maintenance, if you're uncomfortable or unsure, GO TO THE VET! If you're uncomfortable or unsure, DO NOT ATTEMPT! Exotic vets not only perform health exams but also assist with grooming, nail trims, etc.
For the love of all that is holy, please don't go sticking q-tips in your bunny's ears or scent glands if you are not 100% confident!

Other

Spay and neuter your bunnies; female bunnies who are left intact are prone to behavioral issues, “false” pregnancies, and uterine cancer. Male bunnies who are left intact are prone to behavioral issues and aggression.
Avoid laying your bunny on its back - this will induce a paralysis-like state called a “trance.” While your bunny may seem calm and relaxed, it’s actually terrified. The only time trancing is remotely acceptable is to avoid unnecessary anesthesia, as deemed by a veterinarian. Click here to read more.
Find a rabbit-savvy vet in your area before you consider getting a bunny to be sure that you can provide it with the best care possible, especially in emergency circumstances.

First Aid Kit for bunnies

Websites to check out:

WabbitWiki
MyHouseRabbit
Rabbit SubReddit