Start by cover your floor with rosin paper and masking tape to protect against wallpaper paste. Remove all switches and wall sockets. Check which of the corners of the room is the least eye-catching. Start or finish wallpapering there. This is especially important if you are using patterned wallpaper.
The first layer of wallpaper should overlap the corner by one centimetre. Measure the width of the wallpaper roll with a folding ruler and subtract 1 cm from the width. Then mark the measurement (width of the wallpaper roll – 1 cm) on the wall with a pencil.
Walls are rarely perfectly straight. To make sure all the waves are straight, you need to solder the first wave. You can do this by drawing a so-called plumb line on the wall with a pencil and a spirit level.