Using an oil-based primer creates a hard surface whereas a latex paint will simply soak in. Sizing comes next. This important step is the bond between the wall and the paste. It is usually a blue color, which makes it easy to see where you've covered over the white primer. Wallpaper manufacturers will usually include specifications and instructions with double-roll packages.
Most wallpaper today comes with a washable plastic coating.
Vinyl wallpaper is heavy and has a tendency to stretch, requiring special hanging instructions. To make this less obvious, avoid vertical striped patterns. If the trim needs repainting, do this first prior to hanging the paper. Please read it.