When preparing a surface to be painted, the first thing you need to do is to fill in the cracks and holes. To do this you need to apply two coats of plaster compound to the area.
After your plaster has dried, use a sander to lightly sand down the surface until it is smooth.
After sanding, there'll be some fine dust on the surface. You need to dust and clean down your walls before you're ready to start painting.
Before you start painting, remove all of the furniture from the room. Then tape up any hardware and fixtures in the room such as power points, architraves and the floor. This will help prevent paint from spilling on them.
You could pick a colour for a room based on the dominant colour of the furnishings in a room, such as a rug or a painting. You could also work from light to dark, with the lighter colour on the ceiling, a mid colour on the walls and the darkest colour on the floors.
Water-based paints are generally used on ceilings and walls. Oil-based paints, which are more durable, are used for trims, architraves and doors because these generally get more wear and tear.
1 litre of paint will roughly cover about 16 square metres of surface. If your surface is more porous or textured than normal, you may need up to 20% more paint for a similar coverage.