1. I'd get one sized to the dogs ultimate adult size--a 48-inch long wire crate is what I have. Many come with a partition/divider you can use to section off part of the crate while the pup is small, then increase the crate size as he grows. The idea is to NOT give him enough room that he can pee in one corner and sill lay down in a dry spot on the other side of the crate. It should be just large enough to turn around.
2. They don't automatically "know" anything--but you know that. ;-) At 16 weeks, work on focus as the most important thing. That means him being rewarded for paying attention to you. He can't learn anything else unless you can get and hold his focus. Say his name, if he turns his head toward you reward that. Hold a treat in front of your face and when he looks, give it to him. Gradually increase the time you make him hold the look. Then move the treat away from your face and when he looks at you (not the treat) then reward. Fun games like that.
Second most important is recall (come when called.) Teach this on a long line, like a clothes line. Call him, then if he doesn't immediately barrel toward you, you can use the line to give him a cue. Or work on this with two people calling him back and forth to earn treats for comming when called. ALWAYS make coming to you a good thing. Never call him and then punish (or any other thing he hates, like getting his ears cleaned or something.) And while you're training, never call him when you cannot "enforce" that he will come (i.e. on the long line.) You don't want him to have the opportunity to ignore the call. Come means come.
Then move on to sit, down, stand...
Make sure you're also doing daily socializing activities with him too--that means just exposing him to different things--meeting people other than those he lives with (different ages, races, people in wheelchairs, etc.) Expose him to all sorts of noises, go in the car to places where he can see and hear different things (car wash, bank drive through, bus stop, WalMart parking lot, etc.). And expose him to walking on different surfaces--dirt, tall grass, concrete, slick floors, gravel--as many different surfaces as you can.
At this age you should also start a regular ritual of grooming (even if it's just "pretend" grooming) where you touch and stroke him all over, handle his feet and ears, fingers in his mouth, and generally get him use to and relaxed when any part of his body is being touched. It's pretty easy to get a puppy to allow you to brush his teeth, trim nails, clean ears--heck, you can even get a puppy to let you vaccuum him! But if you don't start these things early, you'll have a very tough time when he's older to start these things.
Hope some of this rambling helps...
;-)
Cinco | Jack | Fanny | Ellie | Chip | Deacon