dmcarty did bring up a good point that I forgot to mention, as with wanting to meet a breeder and her dogs before choosing a pup, do the same with trainers. I highly suggest going and just observing class the trainers teach. She was right that sometimes there are good trainers at PetsMarts and there are ones that aren't . The training areas they have now in 90% of stores is a 20x20ft or bigger.
I used to train for them about 2.5 yrs ago, I know that somethings have changed since I left, and that they have lengthened the training that the trainers have to go through before they can actually train on their own, and that's to include 100 hours of training with the head trainer there for supervision and assistant.
Okay sorry rambled a bit. You can find many places to take your pup to obedience school, from petsmart/petco to kennel clubs and private trainers. best thing is what will fit in your budget and what you are comfortable with. So go and observe people training and talk to them. And IMO don't send your dog away to a "obedience boot camp" (they are the kinds where you have no interaction with your dog and someone else trains him/her).