How old is your kitty? Though there is some controversy about this, I think the safest thing is to spay her at or shortly after four months of age. Any later, and you run the risk of her entering heat, and with that comes increased risk of various kinds of illnesses down the line.
As for finding a good vet, I would ask for recommendations from friends you trust, and from no-kill shelters with good reputations. Then go and visit the vets to see what you think of the people and the premises. Ask them to tell you about the procedure, how it's done, and what kind of anesthetic they use. There's a gas that's the same thing doctors use on human children, and my understanding is that it's the safest one for most cats.
Whatever you do, don't scrimp on spaying -- it's major surgery for girl kitties, and it needs to be done by a talented and caring veterinary surgeon. And personally, I won't leave my cats with a vet for any kind of procedure... I stay with them before and after, partly to provide support and partly to make sure the vet and the staff are hyper-vigilant about my cat's care. My feeling is that any vet who refuses to allow this is probably not someone I want to trust with my cat's life.
You might also want to choose a vet who has cats of his own. We've had two primary vets for our kitties, and the first was a very fine doctor and a nice man, but he was fundamentally a dog person. Our new vet is a woman whose greatest personal interest is in cats, and I do feel there's a little bit of a difference, especially for the cats themselves. This "cat lady" is very good at making them feel at ease.
I'm asleep on my feet here, so please forgive my disjointedness -- I'm sure others will be along with better advice. You might PM "StarryEyedTiger" and see what she thinks... she's a vet tech and really knows her stuff.