To have a pre-anesthetic blood panel done as well as a full check up. Make sure your vet has a good ear to spot any sort of abnormalities of a beating heart and that should be it!
It's always nice to find out just what their procedure is for the spaying. Are they using lasers for the incision or scalpal? Are they going to cautorize (sp?) or are they going to suture? Are they going to use injected anesthesia or are they going to use gas?
Try to get specific on the practice and procedure so you feel comfortable while she's at the vet's for the day. And don't forget to breathe!
