Never give a command that you cannot enforce. Another way of saying that is: Always make sure that you have some way to enforce your commands, until your dog is 100% conditioned.
When training new commands–or even enforcing commands that your dog already knows–give the command only once and then make your dog do it. (Just Do It, as Nike says!)
I don’t advise repeating a command over and over again. Even for a puppy. Say it once. Don’t get in the habit of issuing double, triple or quadruple commands.
You need to teach the dog the right way, from the start.
Here is the chain of training: Command – Action/Behavior – Praise – Release.
For example: Say, “Sit,” once (command). Then make the dog sit. (Action/behavior). Then say, “Good dog!” and give her a scratch behind the ears. (Praise). Then say, “Take a break,” or “Free”. (Release). Then do it over again.