Where you have difficulty matching up the pattern on two drops of paper it is likely that your pasting technique is at fault. Under- or over- soaking the wallpaper reduces its ability to adhere to the wall and makes the paper difficult to handle. Follow the paste manufacturer's instructions regarding proportions, mixing and setting times: too thick a paste will cause bumps and lumps, too thin and the water will over-soak the paper, which can cause it to tear. Blunt scissors won't cut a true line, and the edges of the paper will become frayed; keep wallpaper scissors clean by wiping off the blades after each cut. If your wallpaper starts to fall off the wall in complete strips it's because you didn't line your walls first and there are patches of distemper that have made the paste lose its stickiness. The only solution is to take the wallpaper off the walls, clean the walls and, where necessary, apply a stabilizing solution. Then line the walls and re-hang the wallpaper.