How do I remove wallpaper from drywall?
It depends :)

It really depends on how old the wallpaper is, if there are multiple wallpapers glued over each other and how much glue was used.

If the wallpaper is not too old, and was put on in a proper way, usually, a steamer works very well. It has the advantage that it loosens the glue without making the wallpaper to fragile to pull it off. 

I usually try to stay away from chemicals, because they always have some danger for health associated.