It's a reward-based training method. The "special equipment" is one of those little metal clickers or crickets with the tiny piece of flexible metal in it that clicks as you push and release it. You know, one of these . . .
Basically the clicking sound signals correct behavior instantly (getting "Good Dog" out of your mouth takes some time).
To begin conditioning your dog to the clicker, you start with a handful of treats (very small ones - I take the little Nutro training treat squares and break them up into four pieces). First you click the clicker, then you feed the dog a treat. Click-treat-click-treat-click-treat-click-treat as fast as you can.
Then the dog associates the clicker with a treat (this works REALLY well for food motivated dogs like Labs!) You must always have a treat ready, so you can treat immediately after the click.
Once you've established the connection in the dog's mind, you can "shape" his behavior by clicking for actions you like (and ignoring actions you don't like). Call him with great enthusiasm, "Sarge, COME!" When he starts towards you, click and he'll run to you for his treat. Delay the click and treat with each successive call, until he has to come all the way to you before he gets his click and his treat.
Same method for sit - most people shape the behavior with the clicker first, then add the oral command afterwards. One of the fun things we learned in my first clicker training class was to teach the dog to pick up a basket and bring it to the handler. You start by clicking when they sniff the basket - then after a couple of times you delay clicking and they will nudge the basket with their nose - click and treat - then delay again until they fumble the handle with their mouth - and so on. Any intelligent dog will mess with the basket until he figures out what "dispenses the treat" . . . my dog is four years old now, and when she spots that basket she runs to get it and bring it to me! A friend of mine's first clicker task was to train her dog to get into a cardboard box.
Most clicker training people are "positive-only" trainers - my dog is trained with a mix of positive and negative, because she also does retriever training and an E-collar is a must in that line of work because the dog is working so far away from you. But certainly with a puppy positive training is best!
You should be able to Google "clicker training" and come up with a lot of online stuff. Here's one. But getting into a puppy class that uses the clicker is probably the best way.