The below, with some adaptions, is from this site:
http://www.bissell.com/Main.asp?Page_id=46649&cookie_test=1
"Rule #1 Take into account your dogs physiology.
Bladder control begins in puppies at 12 weeks. Most puppies fewer than 12 weeks cannot physically hold urine or stool for more than a few seconds when they are ready to go. After 12 weeks, bladder control is achieved slowly through the next 3-6 months depending on the breed. Toy breeds are the slowest to gain bladder control. What this means is if your puppy is less than twelve weeks old, he will not be able to wait to go outside, will not signal that his bladder is full and will have accidents if he is allowed to roam free.
Rule #3 Housebreaking starts with YOU being housebroken.
When you adopt your puppy they generally have no idea about housebreaking, so you are the housebroken one. You should take them outside every hour for a puppy less than 12 weeks and every 2 hours for an older puppy, unless there are consistent accidents, in which case you can take them outside more often. Don’t wait for a young puppy to signal you as they don't usually start signaling nor have time to wait for you to notice until after 16 weeks of age. When you take your puppy outside and they stool or urinate, then they have earned free roam time in the house until they may need to go again (less than 1 hour for young puppies, 1-2 hours for older puppies). If they don't have a stool or urine, contain them in the house so they don’t make a mistake. This brings me to the next housebreaking rule.
Rule #4 ...If you cannot watch your puppy closely when he is free roaming, put them in the crate or take them outside to eliminate so you know they are “safe” to roam.
Rule #5 Leave water out all the time but feed in meals.
Water should be available to puppies at all times except in the crate. Puppies can get dehydration or water gorging if water is only offered at certain times of the day. Kidney problems can result if the puppy is not allowed to drink when thirsty. Food should be given in meals, generally three meals per day for a young puppy. Offer food for 15 minutes and then pick it up. We know that puppies should have a bowel movement within 15-20 minutes after a meal. This helps you time the bowel movements so that we know when they are coming and you can get them outside at the right time.
Rule #6 Use praise to reward good behavior.
When your puppy does what she is supposed to, praise her so she connects what she did with what you want. Alternatively treats can be used but be careful that you are not giving so many treats a day that your are causing an imbalance in your puppy’s diet.
Most puppies respond best to praise and it is readily available, as well as easy to give out. If your puppy has an accident don’t scold unless you are standing right next to her and catch her in the act. When you find an accident in the house, just clean it up and move on and consider where the error was made. After all it was your fault for not being housebroken (see Rule #3). Never use physical punishment of any kind as that just creates a fearful puppy.
Rule #7 If your puppy is not making progress by 13 weeks of age, check for health problems. Generally after several weeks of consistent housebreaking all puppies start to show some progress. They go to the door occasionally, are able to hold urine more than 1 hour or show other signs of catching on. If this in not happening, ask your veterinarian to do a thorough check of your puppy including a urinalysis. Sometimes young puppies have health problems that make housebreaking difficult or impossible.
Rule #8 Be consistent and patient. Puppies understand things that are done the same way every day. Take your puppy to the same door to take him outside. Using key words such as “potty” every time you take him outside. Hang a bell on the door, low enough for your puppy to reach it and ring it before you take him out. He will come to associate the bell with the need to eliminate and will eventually ring it on his own to signal that he wants to go out. Be patient. All puppies can be housebroken with enough time and consistency."