A bunch of disjointed thoughts:
Gender doesn't matter, but spay or neuter either way. This should be done before puberty.
Make a vet visit immediately for a full checkup. If the cat hasn't been receiving care there may be vaccinations and parasite treatments to do. Schedule the spay/neuter if it hasn't already been done.
Your cat should see the vet on a regular basis. Depending on where you live, vaccinations will be done every 1-3 years. Cats also need dental every 5-7 years, which is a major undertaking.
Know that illnesses can be expensive, especially if you need to see the emergency vet. Cats are good at hiding injuries and illness, so when a cat actually appears sick it is dire and you need a vet right away. It can't wait until payday, so make sure you've put some money away in case of cat-emergency.
Do not declaw. Many vets won't even do it anymore. If you insist on having a declawed cat, adopt one that already had it done. They sometimes have behavior problems though, which is the common reason why declawed cats are surrendered.
If you're super fond or protective of your furniture, don't get a cat.
You'll need at least one litter box. Two is better if you have the space.
Some cats like vertical scratchers, some like horizontal. Surfaces matter too. There is no way to know until you try them. Ours loves his Cosmic Alpine scratcher, which is made of cardboard and at an angle.
Do a little research on cat foods and best feeding practices. We made the mistake of buying a cheap dry food and our cat developed a health condition. Now he is on a special medical food (both dry and canned) that costs more than a decent food would have from the start.
If you have friends that are allergic, some of them won't be able to come over anymore. One of our friends takes medication and I always do a thorough cleaning, which helps. Another friend can't even be in the door for more than 5 minutes without puffing up.
On that note, be sure that no one in your household is allergic. Go to the shelter and rub your face right on a cat. That should get a quick answer. ;-)
If you have kids, they have to be strictly monitored and have proper behavior enforced. No chasing, no cornering, no pulling tails, no picking up if they are too young to do it properly. Google for "what is my cat saying" to learn about body language. Cats give noticeable warning signs before they scratch or bite.
Check your local laws. In our area, cats have to be licensed annually. To get the licence, you have to show proof that they are up-to-date with their rabies vaccination. Cats here are also subject to leash laws, which means no free-roaming outdoors. You can train kittens to a harness and leash, or you can have an outdoor enclosure (should have a roof, they climb).