Seriously, everybody here has given you good advice, BUT it really depends on the age of the walls, the age and type of wallpaper, and how much you are talking about.
Spike wheel and DIF are good products, for newer houses and relatively thick paper. But, older paper, on plaster walls or 70s vinyl paper? Save yourself the heartache - rent the steamer. Yes it costs a little money, but rent it don't buy it. With the wheel and DIF you can do a wall a day. With the steamer you can do a room a day easy. If you are doing a whole room I vote for renting.