No two verbal cues are more important than "leave it" and "drop it" with a puppy. As you get out and about, undertaking the much needed socializing; you realize just how much stuff is on the ground. I've been going to many different places and now parks that Elsa has had her last set of puppy shots and it's all about keeping her safe by not letting her devour everything in sight.
We started both of these behaviors right from the get go; we have bark in our yard which was a big concern. Just last year we put in several new gardens with the finishing touch being bark. Before we got Elsa I clearly remember gardening and thinking to myself "this might be a really bad idea." Of course she was at first fascinated with it; she was never outside without us so we were able to nip the "bark" issue in the bud.
"Leave it" is used before a dog has an unwanted item in their mouth; that means you have to be on the ball. Keeping one step ahead can be tough when a puppies head is constantly on the ground. We started "leave it" before actually sitting down to learn it. That meant a loud "leave it" was used just to get attention and then getting the reward in there quickly. Basically it is all about "don't eat that and I'll give you a goodie." In the beginning you must reward every "leave it." As the dog gets older you can wean off of treating every time saving the big and impressive "leave its" for the rewards.
"Drop it" is used once the dog has something in their mouth and you want it out. There are times when you are simply going to haul it out of there quickly but you must also do a trade. If you only use a physical emptying of the mouth each time, your dog learns to run and swallow, a dangerous thing. It is important to also use drop when you can return the item; this helps to lessen the run away reaction as well. When your puppy is chewing a safe toy, ask them to drop, give them a treat and offer them the toy again.
"Drop it" is started with a bribe; your puppy must consider the bribe good enough to spit out the bad stuff. By offering a treat trade you are able to get into their little brains and erase the run away and swallow response as well. Of course getting to them before they have something bad in their mouth works best; that way you can reward them for not picking items up.
Both of these behaviors are essential; otherwise you could be doing a great deal of chasing your puppy down and mouth hunting for dangerous items. This in itself instills the reaction to run; getting rid of it is fairly simple, it just takes work.