Often carpenters will make quick work of cutting fiberboard sheathing by making their cut marks with a chalkline instead of a carpenter's pencil. Hook the end of the chalkline on one end, hold down the other end, and snap to make the line. The same idea can be used on other sheet material.
Stir wallpaper paste for longer than suggested by the manufacturer to ensure that there are no lumps. A wooden dowel makes and ideal stirrer. Also stir the paste from time to time during wallpapering.