Try looking up TrainingPositive on YouTube or visit their site (trainingpositive.com). It's an amazing source of tips on how to use positive reinforcement.
I've only slapped Hamlet a couple of times when he mouthed me and I wasn't paying attention and didn't see him in the vicinity. Since we have only used positive reinforcement (no consequences harder than a stern "No," quick leash correction, or a firm but gentle tap on his hindquarter area to snap him out of a distracted state), he was completely baffled these two times I accidentally smacked him. I don't think smacking him (or any dog) was really motivating... He was just totally confused.
I think of it this way: are you more into the idea of winning or not losing? If your boss tells you you are being considered for promotion if you can improve X, Y, and Z performances, are you more motivated than if your boss tells you your job security is in question if you don't improve X, Y, and Z?
Positive reinforcement has done even more for me and Hamlet's relationship than its proponents billed it for. The promise of reward for his obedience and focus has made it possible to put him into a working frame of mind in a second's notice without touching him. He has even improved in areas of training with no input from me, because if he wants anything in the world he knows an established recipe for success: calm, focused, giving eye contact, and following instructions. I used to hold his bowl until he sat and gave me calm eye contact (he is the youngest of our four and gets fed last, so all the dogs are chowing around him while he waits). Just last night we discovered we could put the bowl at our feet and he would give us the same distance and response until we slid the bowl to his feet with a release word ("Okay!").
Sorry for the diatribe, but I can't recommend positive reinforcement (or specifically I use "operant conditioning") enough.
There are some pros here who will probably give you more instruction and less heartfelt inspiration, but there you have it, my two cents (maybe twenty...).
PS I use the same cue as Tab from TrainingPositive ("Yes!"). I binge-watched a bunch of his videos and have found I exactly copy his tone of voice--both calm and jovial, consistent every time. It is so hard-wired into Hamlet now that he seems to get a little puppy high of calm happiness every time I say it. It is so ingrained that I accidentally said the word Yes while in conversation with someone in a very similar tone and he whipped around and sat for his treat.
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