Even though you've only been around other pets briefly, this tells me a lot. The fact that you'll sniff a quieter pet & not hiss at them is a VERY good sign. You hiding from a hissing cat or barking dog is also a good sign and also VERY smart. The first shows that you're interested but don't feel threatened. You running is just a natural reaction to a new pet. The second shows that you're not aggressive.
An uninterested cat will not come out or will hiss telling the other animal that this is HER territory. An aggressive cat would hiss or even attack another animal on her turf.
(Honestly, I meet a new ANYTHING and I start hissing!)
You being very active says you will probably do well with a lively kitten or younger cat. I would suggest getting a male since we tend to adapt easier to new siblings and girls tend to take much longer to get along. (There's a reason you female cats are called QUEENS!)*
But if your person gets a female who already gets along with other cats, I think you'll be fine. It just might take a little longer for you two ladies to get along.
* This comes from Toms having wider territories that traverse the areas of multiple females in the wild. Queens keep to smaller areas because they have to keep the kittens safe from predators and make sure there is enough food. Now Queens will work together in a Colony of Feral cats so it is possible for them to get along too, it just often takes longer.
When your owner brings home the new bundle-o-fur, keep in mind all the newness that the new cat is having to deal with: an unfamiliar place, an unknown person & an unknown cat. For this reason, it's important to take it slow & remind your human that if things aren't going great, she can always take a step back. (Just like with humans, some cats adapt to new places easily while it takes some time with others.) Here are some suggestions to make the transition go smoother...
1) When your human brings the new kitty home, be sure she has a separate room already set up. It can, and possibly should, be a bathroom. Items needed: Bed / smooshy place to sleep on, litterbox, food & water bowls & toys. (If the kitty has anything that is coming with them, put it in the room since it will smell familiar.) Have your human put the kitty in that room so you can stay separated for at least the first night, probably longer.
If she adopts a kitten who has to have a spay/neutering surgery, she will want to keep the kitty in the room for at least a week before any intro can happen. It's important that they fully recover.
2) Have your person put treats on either side of the door so you can smell each other while eating something yummy. (Also, TREATS!!!)
3) She can rub a cloth (washcloth, hand towel, etc) all over you and the other cat, making sure to get the face by the sides of the mouth / cheek areas.* Have her put the cloth under the opposite cats food bowl. Same concept as the treats, you smell the other cat while eating & associate that smell with something good - food!
* It's kinda like an extreme petting session. I LOVE it! Though I might bite the cloth if my human does it too long.
4) Tell your mama to pay attention to how you and this new INVADER (I mean, cat friend) are reacting to each other through the door. If you're ignoring each other, this is not a bad thing. If there's a lot of hissing, she will want to take it slower. If either of you are marking the door with your faces, this can be good or bad. If you're poking their paws under the door and nobody is hissing or acting scared, this is good. If you're playing with each other's paws, that's GREAT!
5) Getting ready for the intro.... Okay... so this next part is for your mama's safety. Tell her to have a broom &/or a large, not too flexible, bit of cardboard on hand. This is VERY important because if you cats fight, under no circumstance does she want to put herself between two cats. She WILL get hurt. If a fight breaks out, she will use the broom/cardboard to separate & guide either you or the other cat back into the bathroom. (It doesn't have to be the new cat.) Also, if she can close the bedroom door, do so. She really doesn't want to have a fight under the bed. (Us cats can be VICIOUS!) Tell her to try to blockade any under the couch or any other small and confined area as best she can. The most important thing is for her to remain calm. Remind her that you and the other kitty will feel her tension and will reflect that.
6) Before the intro.... Tell her to spend as much time as she can cuddling and playing with each of you. This will reassure you that she's not replacing you and it will let the new kitty know s/he is loved. Also, she will want both of you to be low energy when you first meet each other. Trust me!
7) Without making a big production of it, at a point when neither of you are really paying attention to the door, she should open it and walk away. She should have her broom/cardboard nearby & be watching, but this is cat time. Tell her NOT to try to urge or force either of you into each other's space, she should just let you do it on your own. She should make sure she has time to sit there for a while. The new cat may come out slowly, sniffing everything as s/he traverses the new space or it may be a run. (Each cat is different.) You, Machete, might be more interested in getting into YOUR bathroom rather than interacting with the new cat. If this happens, this is GOOD.
8) When you do interact, if you hiss at each other, tell your mama not to fret. If you ignore each other, that's fine. If you play, that's GREAT! In fact, the only time your mama should intervene is if either one of attacks the other. That's when she uses the cardboard or broom to back the attacker off.
9) Hopefully, this goes well and she's not closing a cat in the room to keep you or the other cat from fighting. But if that happens, tell her to take a breath, drink some rum (or beverage of her choice) and try again another day. Cats who initially fight can eventually become friends, so don't take it as a bad sign. It just means there's more work to do.
10) If you do get along (yay!), she will still want to have one of you hang out in the room when she's are gone. If she can switch it up, that would be great. This is what is known as side-swapping. It will allow the new cat to explore their new home and you to get used to ALL the smells (even the litterbox smell) of the new cat. And, not to be gross, but you will both probably pee or poop in the other cat's litterbox. That's good!
If there are any accidents at this time of transition, just clean it up. It doesn't mean you're regressing or that the new cat is going to be trouble. It just means that there was an accident. One thing she can do to prevent more is cover / hide the place where the accident happened for next few days.
Good Luck!
Meander
A note from Machete's Mom:
Even though I've already heard or read some of these things, its the extra little additions that actually make the tips useful. (Like not just using cloth, but making sure to get the sides/mouth/etc) Not to mention the personalized cat personality tips and experience.