Normal Puppy behaviour exploring her world with her mouth.
How we dealt with it:
nothing left at puppy height that we wanted keeping pristeen.
Teaching leave and swap.
Leave: When to use: when you see the pup going for something that they shouldn't have (before they have it)
How to teach: Have a really really tasty treat in your hand, hold it at nose level they will sniff and sniff and lick at your hand to get the treat. The second the nose comes off the hand praise "Good leave" and give the treat. Build up the time the nose has to be off the hand before the treat is given. Add the command at the start so after a few snuffles say leave. Once they have this more on to an item on the floor, get them in a sit (this gives you a cue for when they are going to go for it as the bum will come up)
and put the treat down, and say leave. After a few seconds say good leave, pick the treat up and give a different treat than the one on the floor.
Swap: When to use: Pupster already has the item in the mouth.
how to teach: Don't go towards them! This will turn it into a chase game. Start cooing over what you have in your hand, make it the most interesting and fun thing ever "Ohhh yummy, how great! look at this!" this gets their attention and your thing looks better than their thing (as soon as they know you want their thing it's game over!) get down on their level, they might at this point come towards you if you are convincing enough! keep talking about your thing, don't look at the dog apart from out of the corner of your eye look at your object. Turn half away from them as if your trying to hide it. then notice they are looking, look at them and then back at your treat a couple of times. Then add the command swap, and hold the treat out for them to see (if they are really interested the other thing will be on the floor by now DON'T PICK IT UP yet) when they have come over if they still have their thing say swap and hold your thing out and they should drop theirs. Only when they have your thing and are engrossed with that do you SLOWLY get the object they shouldn't have had. You can practice with their toys, and give it back to them after you have had a look at it etc.
HTH
Swap: When to use: