GAME - Just ONE thing

 Dogs have great hearing - they can hear you just fine, you don't need to yell commands. If a dog doesn't obey when you whisper to him, it's because you haven't trained him enough, not because you need to raise your voice!

Have a sense of humor--you will need it! 

Research your breed.  Then go meet as many members of that breed that you possibly can.  That way you can get a true feel for the type of dog that you will be sharing your life with.  There will always be dogs that are outside the "norm" for a specific breed, but the more that you meet, the better your chances of choosing the breed that fits in your life perfectly.

 To add to Amanda's research suggestion.... foster a member of the breed in question, if you can. Living with a dog is *totally* different from meeting them in or out of their homes. It's LOTS more fun, but you see a different part of the dog. You get the whole picture, instead of just bits and peices.

 Get your dog used to being restrained - by your body, by a leash, in a crate, or in a room alone.  It's a necessity for health and safety and easier for all involved if the dog isn't whining constantly or flipping out. 

Be a tree.   If you do not wish to be pulled around on a leash, rushed on stairs, crowded at doorways, dont allow the puppy to do that in the beginning.  Stop your own movement and be a tree.  When the puppy looks at you with a question, call their name and get them close enough to pet.  Then proceed.  If you have a longer period of time available, just keep stopping and waiting until your puppy gets beside or behind you.  If you dont have time to train the behavior at that moment, get a hand on a collar (or take out the trusty little leash you always have in your pocket), and snap it on.  Puppies who rush and pull and forge can be frustrating as adults.  Remember, if they do those things, its is because they learned what you taught, not what you intended.

 Catch your dog doing something good, not just something bad.  If you remember to praise your dog when he's laying calmly on his bed, he will present that behavior more for you, then if he only gets attention when he's acting like an idiot.

 To expand on MRV's rule:  ANYTHING a dog is taught as a pup is going to be hard to unteach as an adult.  So, jumping, pulling, mouthing, pawing, lunging, knocking the food bowl out of your hand before you manage to put it down, barking at strangers, anything undesireble as an adult, should never be encourgaged as a puppy.

 Teach your puppy that you are THE most interesting thing on the planet!!!!

Play hide and seek with your puppy, it is one big step towards a reliable recall command

Reward, reward and reward again for each time a puppy is caught doing something he should.

Start socializing and positive training at home, but get to a positive puppy class early (one where there are no choke chains or electronic collars used), before your pup's socialization period ends (optimal socialization period for pups is age 8-12 weeks, 16 at the outside, and I think that's stretching it).  These links will help you get started.  The first has lots of links to puppy behavior questions.  The second contains a series of free training lessons.

http://www.diamondsintheruff.com
 

www.clickerlessons.com

treat your puppy like he's an 800-pound tiger. If it isn't cute for an 800-pound tiger to do, then it's not appropriate for your puppy to be doing it either.

Expanding on the Tiger.... if an 800 pound tiger can be taught to co-operate, then you need not use force with the puppy.  In the word of Clothier; "Co-operation weighs nothing".