The best method is to have someone else do it.
A wide painting spatula or spackle knife is a must for this work.
Most all methods recommend wetting the existing wallpaper with at least water to loosen the glue adhering to the wall. Newer, strippable papers will allow you to peel the entire sheet, or most of it, from a starting corner. Let the water work in for about a half-hour before attempting removal.
There are commercial stripping chemicals that can be used for really difficult paper, but you should be able to get good results with a mixture of white vinegar in hot water (not scalding as you need to work with it). Apply the water with either a spray bottle, or clean paint roller to really drench the paper. Be sure to put towels down to protect floors, rugs, and furniture.
If the wallpaper you have is water-resistant, than you will need to score the paper to get the water behind it. You can use a utility knife, but run the risk of leaving gashes in your wall that will need another prep step.
There are also steaming products available and I have heard of people using a steam clothes iron to assist in removal.
Here are some tools and products to help: