If your idea of a cat is a 20-pounder with no free will who just sponges up luv, how do you spot that in a kitten?
Or if you want a ruthless killer, how do you tell which fits-in-the-palm-of-your-hand animal will grow up to hunt?
Ideally, watch the litter play together, and throw toys/balls, etc. Also hold/cuddle each. You can get an idea of the personality from that.
My cat has very high play drive. Definitely not a slacker.
the more you handle, the more they will look to you for attention and tend to be lap cats…I had the task of capturing MANY offspring of ferals that moved into my barn…the ones that respond with coming back for loving, climb up your pants and sit on your shoulder while the others are scampering around are the ones I would ID as more couch potato type…of the 20-some kittens I had here last summer (ALL were tamed,socialized,fixed, and thankfully, most adopted)…the ones who seemed the most “needy” as babes are the ones that are still running to me as soon as I come out, climbing on me as soon as I sit, even if it is on the tractor, 2 will stand on hind legs and paw (no claws) my leg to be picked up and cuddled , and the same 2 love to crawl on my shoulder and just sit and observe…
Yep, it’s the needy cuddle-ers who morph into the lap cats/slackers. They are most often adorable sweet males, too. 
come to thinkof it,yep,most are males, and many are orange OR black
Lazy fatty = black & white male
Ruthless hunter = torty female
I knew my feral tuxedo male was a lover when I put food out & he he purred & layed down in the dish.
My lazy love bug behemoth, a huge neutered male, is also a ruthless killer if the prey is of sufficient size - he will not hunt mice but goes after gophers, ducks and other gamebirds. My other ones that just laze around and are attention seekers are death to mice although Louie retired himself and now only hunts softer places to sleep and he earned it by killing every mouse that dared to enter the house. I only have one non-hunter and that is Blue. She was born in the house and had nothing to learn on and ignores toys as well, no drive at all. I’ve never noticed any difference between males and females as far as hunting ability goes - neutered toms hunt just to kill as do spayed females.
As Jetsmom said, how they interact with you and each other can tell a lot.
I don’t think they’re mutually exclusive though – I’m fairly certain they can be both excellent mousers but complete cuddle bugs. My little guy would probably be like that – he’s a lover and a fighter. 
The best way to get a certain trait in an adult cat is to adopt an adult cat (not to mention, you’re doing a good thing-kittens find homes fairly easily but adult cats not so much).
However, you can tell a lot from interactions with the litter-not only how they interact with people, but also with each other. Also keep in mind that spaying/neutering as early as possible (and well before puberty sets in) can make them mellow out a lot. Kittens learn to hunt from their mothers, so if you want a mouser, look for a litter from a good mouser and don’t wean them too early as mother will teach them to hunt as she introduces them to solid food.
Size is a lot harder to predict in young kittens, though if they’re slightly older, my vet’s rule of thumb is that their weight at 4-5 months of age is approximately half of their adult size (assuming they’re at a healthy weight at both stages).
20 lbs is a BIG cat. If you really want one that big, you should look at Maine Coons or crosses (do Bengals also get that big?). For most cats, 20 lbs is not a healthy weight (my cat is BIG and the vet wants him at 12-12.5 lbs). Just like in people, being overweight can contribute to a myriad of health issues, from arthritis to diabetes.
As a side bar, when do kittens usually reach their full growth? I know it differs between the breeds if purebred, but what’s the typical for the average moggie? I’m going to need a shrink ray for mine if he keeps getting bigger…10mos old and already a behemoth.
Well, with my 20lbs behemoth, the day after he was born, he was half again as big as his three littermates. He’s HUGE. Not just fat, though he’s fat and lazy, but he’s always been big, with heavy bones and a long body.
No, I have no idea why. He had three litter mates, a female and two other males. One other male was also big and fluffy, but more like 10lbs. The others were average to small shorthairs, and the mother was a seven-pound shorthaired tabby.
And on the other side of the coin…my 22lb monster cat (a sweet-as-sugar cuddly orange-and-white mamma’s boy) was the runt of his litter of three.
He was still the runt at 10 weeks when his sisters left, and they were both already quite large. He hit 1 year old and somehow just got gigantic overnight.
His mom is a solid 14lb-er, with gorgeous long hair, a dumped barn cat.
It is impossible to go wrong with an orange cat. Period.
I couldn’t even tell the difference between the bunch of them when they were very small. All grey. As they got bigger we started seeing the coat patterns and the personalities came out - Genghis is our 13 lb slacker and has been since he was about twelve weeks old (not 13 lbs but a slacker). I’d say adopt an adult cat, only one out of ten adoptions is an adult and they need us just as much.
[QUOTE=FineAlready;6915622]
It is impossible to go wrong with an orange cat. Period.[/QUOTE]
THIS…Orange kitties are the best!!
My lazy, love-bug of a lap cat, big boy is my big orange tabby. I’ve had lots of kitties, but honestly (and don’t tell the others) he’s the best cat I’ve ever had. Super friendly, super lazy, and really talkative. I loff him. The best mouser/chipmunker/birder was my tuxedo boy - but he was small (only weighed 8 pounds at the most). We always assumed he must’ve been the runt. Of the 4 currently in my home, the must prey driven is my tiger striped female. She’ll attack anything: light spots, bugs, shadows, moving toes, other cats, etc.
[QUOTE=ReSomething;6915659]
I’d say adopt an adult cat, only one out of ten adoptions is an adult and they need us just as much.[/QUOTE]
Really? That surprises me. I mainly see adults at the shelters… so they keep a swarm of kittens in the back? And our family has always adopted adult cats.
I also had a male runt of the litter turn into a behemoth slacker.
How do you see the “Lover AND a Fighter” combo in a cat?
