you can go anytime, depends on what you want to do. most insurances have an age of either 2 or 3 for coverage to start. as long as their are no problems visually, i think seeing a baby is more for informational purposes, kwim. we had an injury to a tooth so my daughter went at 18 months. it wasnt covered but i was actually happy we went at that age. then every 6 months. at 3 yrs old, at our last visit, she sat in the big chair all by herself(previously she sat on my lap) and opened her mouth. she was a little scared with the flouride treatment but did great. i personally, after seeing her go at the different ages, highly suggest going by 2. its very important to get her used to it and at 3, children are more aware of choice where at 2, they dont realize as much they can say no.
i highly highly recommend going to a PEDIATRIC dentist who is good. no matter how good a dentist is, you want someone used to the antics of kids, and someone who knows when to be engaging and when to be stern. i believe it takes a certain kind of person to be able to deal with this, and have heard horror stories from people taking their kids to a "great" dentist, who apparently wasnt so great with kids.
yes, just get one of those baby toothbrushes and brush 2 times a day. it is needed for the health of your teeth but also gets the child used to brushing in general. good luck!!!