Spackle and sandpaper the wall to smooth any imperfections, then apply a coat of wallpaper primer. While it dries, cover a long worktable (or just the floor!) with a clean plastic painter's tarp. Make sure your hands are clean, too.
If you're papering a whole wall, cut vertical strips 4 inches longer than the wall height; once the paper is up, you'll trim the excess. Arrange wallpaper strips side by side on the floor to ensure that the pattern lines up correctly, gently taping them together with painter's tape to temporarily secure them. If you're making a shape (as with the headboard or sconce backing plates), cut it out on a cutting mat with a utility knife.
Use a tape measure and a pencil to mark where on the wall the paper will be placed. For example, mark the top edge of a chair rail or sides of a rectangle.
Pour premixed clear wallpaper glue into a paint roller tray. Use a small paint roller to apply it quickly and evenly to the back of the paper. (Some wallpaper comes prepasted, so you can just dampen it according to the manufacturer's instructions.)
Now apply the paper one strip at a time, smoothing each onto the wall from the center outward using an 8-inch plastic smoother. For long strips, use a stepladder and work from the top down; have someone hold the other end as you position it (use this same method for wide chair-rail strips). The seams of side-by-side strips should butt against one another, not overlap; make sure these seams lie flat by using a seam-roller.
Once a piece is up, you have about 10 to 15 minutes to perfect its placement. Carefully push any bubbles out toward the borders.
Wash off excess glue with a damp natural sponge, continuing to smooth the wallpaper as you go.
Celebrate with a cocktail.
Both swear it was not only doable but fun (come on, would these faces lie?). "Just don't go it alone!" Shane warns. Having a friend on hand makes it much easier to maneuver long, wet, gluey swaths. His other tip: "Stay calm; you'll be able to adjust things as you go. And if something ends up a little off, it'll just add to the charm."
Here are the materials and instructions you'll need to get the hang of it.