For the first 3-4 days, withhold treats. There will be plenty of time for that later. In the very beginning, dietary changes are not recommended because they are already a tad stressed from all of the recent change.
Whatever you choose to use - get plenty! I like tiny chewy treats because the pup won’t spend a great deal of time chewing. Also they are easy to keep in your pocket so you have them handy all the time. Don't treat "just because". Treat to reinforce good behavior. If puppy is sitting quietly relaxing, give her a treat and tell her Good Girl. Any time a desired behavior is observed, treat and praise, using the “name” for that good behavior ... Good sit! Good down! That helps them associate a
command with praise, and learn their words.
It doesn't take them long to figure out good behavior = something tasty. As they get older, I just use plain old Milkbones.
Also find a high value treat (not meaning expensive, but meaning something they covet) to use for training ONLY. This keeps their attention longer during a training session, which should be kept short and sweet, but frequent. 5 minute mini training sessions in the beginning, as their attention spans are very short as puppies, and they become distracted easily. As they get older, lengthen your training sessions.
I like the Hollywood Stars from WalMart - super cheap, and the puppies love the taste (mine love the liver flavor, but they are fond of the yogurt ones as well). I also buy hot dogs in the giant pack. Take a half hour to cut them into tiny bite size pieces (and I do mean tiny ... I cut a quarter inch round, then quarter it) - they don’t need much - just a “taste”. Then I microwave them, and freeze in small portions in little sandwich bags. You’ll go through them faster than you think!