Look for a pediatric dentist. Most regular dentists won't see a child before age 3-4 and don't have child-friendly offices or practices. But a pediatric dentist specializes in treating children and should have a much better office set-up, encourage parents in the exam room, etc.
I noticed some dental issues with dd a couple months before she turned 2 and really had to search to find someone who would see her. It turned out to be a good thing I was so insistent, because when we got x-rays, despite having an excellent diet, dental habits, etc., from the very beginning, she had 8-12 cavities. She has a genetic enamel defect. (Thanks, Dad! Thanks, MIL!) We were referred to a pediatric specialist. Catching them early made that initial treatment much easier.
We started ds with a pediatric dentist as a toddler. His first few appointments involved him sitting on my lap, the dentist explaining what the different tools are for (and giving them silly names), and getting ds used to having a mirror in his mouth for a few seconds. They just peeked in, got a visual, and encouraged good dental habits. After, he got stickers and a new toothbrush. We slowly worked up to a regular checkup at 2.5 years old. The goal was to get him used to going to the dentist, comfortable with it, and make it as non-traumatic as possible so that he'd be willing to come back twice a year without feeling nervous.
Here are the things I look for in a good pediatric dentist:
*encourages parents to be in the exam room if they want to be
*is board certified or working toward it (it takes years to get board certified, so being "in process" is not unusual and is still a good thing)
*does not use restraints
*offers mercury-free fillings (composite fillings)
*has a child-friendly waiting room
Ours is fine with siblings coming to appointments and being in the exam room. Digital x-rays would be nice, but they're expensive for an office to adopt, so I keep an eye out for that but I don't base my final decision on it. Our new dentist also has hospital privileges, which has turned out to be necessary for dd, so I will look for that in the future, too. But that's probably not necessary if you don't have a child in the high-risk category.