GET ONE IN A LARGE CLINIC TYPE PRACTICE. Then even if yours is booked, you can get in to see SOMEONE for that random middle of the night ear infection or minor emergency. We go to a pediatrician in a large group owned by Texas Children's Hospital. If our doc is booked or on leave or whatever, we can get an appointment with any available doc at any office in the city if we need one. That is INVALUABLE.
Also, find out which hospitals give that pediatrician admitting privileges and which ones accept their referrals. For example, our docs have only one hospital up here that they use for admissions, and then of course Texas Children's will take their admissions and gets all their referrals (which is perfect since they are the best). God forbid, if you need your child admitted into a hospital for any reason, you want one close to home and one that will allow your pediatrician to direct their care.
Just my two cents.