The answer to this question is quite simple! The minute you purchase your new pet. An eight week old puppy can learn to sit, lay down and stay.
You should never allow any behavior now that you will not happily except when your puppy is full grown.
If you do not want your dog to jump up on people, make sure they are always sitting politely in front of you when you greet them or whenever they want your attention. Do not reward them with being petted until they are under control.
If you do not want your dog to beg at the table, do not feed him scraps directly from the table EVER! Always give any table food after dinner is done and always put it in thier food bowl.
If you do not want them in certain areas of your home, teach this the day you bring them home. Simply let the puppy follow you to the door way of the room that they are not allowed to enter. As you cross the door way, quickly turn around, stomp your foot at the puppy and say "Wait". If they try to pass through pick them up , set them behind the door way and firmly say "NO". Continue this until they sit back - even for a quick minute and praise them. With consistency an 8 week old puppy can be trained without the use of annoying door gates. You will have to try to entice the puppy to follow you past this border in order to correct him. Never use his name to call him over this will only confuse him. Once he is consistently staying out of the room, you can roll a ball or toy past the border and correct him if he passes over. By teaching boundaries in your home you will be able to teach them outdoors as well. This is helpful in keeping dogs away from gardens or the road.
You can also teach your dog to go potty in only a certain area of your yard in order to keep the rest of the yard clean. Simply take him to the special spot everytime you take him outdoors during the housebreaking period. Never let him go anywhere else in your yard. As he gets bigger and goes out on his own, you should reprimand him if he goes somewhere other than the specified location just as you would when he has an accident in your home.
If you do not want your dog on the furniture or beds as an adult do not let him sit in your lap when he is little.