Applying Wallpaper to a Ceiling
When wallpapering a room the ceiling tends to be the first area to start on. Starting at a wall with a window, move from the window across the room with subsequent lengths. 
First thing to do is, mark guidelines on the ceiling to line up the lengths of wallpaper, making them run parallel with one wall and at right angles to the opposite walls. For best results the guideline should be within the wallpaper so that no lines are visible on completion.
Be aware of any light fixtures in the room and make sure the electricity is turned off at the mains before starting.
Once the guidelines have been marked, you are ready to prepare the wallpaper. Apply the paste to the wallpaper and fold the lengths in a concertina style and allow the paper to soak up the paste. When the paper is soaked, carry it draped over one arm to the starting point of the guides on the ceiling. Keep the paper held up using a pole or broom then unfold the wallpaper and position it inline with your guides. Slide the paper into position and smooth out any bubbles evenly using a paper hangers brush. At each wall leave an overlap of a centimetre or so. The overlap will be covered later and will help to line up the walls. Continue using this method to cover the entire ceiling.
Applying Wallpaper to a Wall
The first step in decorating your walls is to estimate how many rolls of wallpaper are needed. Measure the walls and write the height and width down so you can work out the area. you can then work out from this how many rolls you will need by looking at the amount of wallpaper you get in the rolls and you will have to think about having enough to carry on a pattern if that is the kind of paper you are using.
Before hanging the wallpaper, make sure there is no previous wallpaper remaining and fill any cracks or holes in the walls making sure there are no dents or bumps.
Now measure the distance from the top to the bottom of the wall and mark out then cut that length from the roll. Leave an overhang of about half a centimetre and only cut one length at a time to maintain continuity. Now the lengths of wallpaper have been measured and cut they are ready for pasting.
You are now ready to apply the wallpaper. Start by lying the lengths of paper face down on a table. Take your paste mixture and apply it from top to bottom in a, spreading the paste evenly and taking it as close to the edges as possible, taking care not to get paste on the front.
To avoid any blistering it is best to make sure that the paste is applied evenly and covers the back of the paper completely. If blisters start to appear once the wallpaper has been hung it is best to remove the pieces affected. Blisters occur when the wallpaper becomes stretched and if left they will probably become more apparent.
You are now ready to hang the wallpaper. Mark a long pencil line using a spirit level and use the marking to line up the lengths of wallpaper. Try to avoid placing the paper over the mark (instead place it parallel to the lines). To apply the wallpaper un-fold the top part of the piece and stick the paper loosely to the top of the wall. Position the paper about five centimetres over the top of the wall and push the wallpaper into place. Once the wallpaper is hung, use a paperhangers brush to smooth any bumps out. Unfold the bottom five centimetres and apply the other half of the wallpaper to the wall, smoothing out any further bubbles.
Now the wallpaper is in position, use scissors or a small blade to cut off any excess. Finally stick down the edges of the lengths and remove any left over paste with a damp sponge.
To apply wallpaper on corners, you need to measure the distance from the last length of wallpaper applied to the corner required. Next, cut a length of paper downwards to the width measured adding an inch for overlap onto the measurement to make an overlap which will fit the corner. Bear in mind that if the wall is unevenly plastered then an excess overlap may be needed to make up for it. Apply paste to the back of the wallpaper evenly, taking care to apply the paste evenly into the corner. The excess length from the previous cut should be pasted from the corner as this will make the join less prominent.
When applying wallpaper close to electrical sockets make sure to turn off the mains power first. Alternatively, you can loosen the fitting from the wall (ensuring that the mains electricity is disconnected first) and fold the excess paper beneath the fitting. Circle shaped fittings can be solved using a similar method. This can be achieved by cutting a star shape in the paper around the fitting, however this can prove awkward and mistakes may affect the fitting. As this involves an electrical fitting care must be taken particularly with the application of paste.
An Alternative, Pre-pasted Wallpaper
If you don’t have much experience or are pushed for time, pre-pasted wallpaper may be best for you. Cut the wallpaper and prepare it into a loose roll. Then, instead of brushing on paste, take the paper and allow it to soak in a bowl or bucket of water for roughly a minute (directions will be included on the packaging as times can vary across different makes). After a minute or so the water will have reacted with the glue and will be ready to be taken out. Take care to remove the rolls slowly so that any surplus water can run into the trough instead of being absorbed by the paper. Apply the paper as usual and then wipe down the surface with a clean, dry sponge to soak up any water left.