The trouble is that the ceiling should be decorated before the rest of the room, because of splatters and drips, so if it’s just the ceiling that needs attention, you’ll have to decorate with care.
Ceilings get stained by things such as water leaks, candles, light bulbs, and smoke from real fires. Scrubbing the stain and repainting can work, but you often need to use a (solvent-based) stain-block paint, such as Polycell One Coat Stain Stop or Ronseal Anti-Damp Paint first to prevent the stain from reappearing.
As these paints can be pretty thick and so hard to apply neatly, you may want to try using an emulsion that blocks stains instead, such as Polycell 3 in 1 BaseCoat or Polycell Crack-Free Ceilings if you have a large area to cover. These don’t conceal all stains but are much easier to work with.
When using a solvent-based paint on a ceiling, it’s essential to wear protective glasses or goggles because you don’t want to risk getting the paint in your eyes.
Wearing goggles (and a shower cap) is a good idea whenever you’re painting a ceiling because the paint will splatter all over your face and hair. You can avoid this by slotting your paint roller into an extension pole, so you paint standing on the floor, rather than at the top of a ladder. This is easier but makes it harder to get a good finish, because you can’t see the bits you’ve missed and the mistakes you’ve made so easily from the floor.
The easiest paints to use on ceilings, especially if you’re not decorating the rest of the room, are semi-solid ones, which splatter and drip less because they’re not runny.
You could also use a roller that has the paint inside it, such as the Bosch PPR 250 electric paint roller. This pumps the paint from the tin to the roller via a tube, so there’s almost no chance of drips and splatters.
If the ceiling’s less than perfect, make sure you use a matt paint because one with a sheen will highlight the imperfections.
Ceilings are prone to hairline cracks, especially if there’s movement above, and these can be hard to eradicate long term.
For large cracks, use a hairline-crack or flexible filler, but for small ones, again try Polycell 3 in 1 BaseCoat or Polycell Crack-Free Ceilings, which will fill hairline cracks as well as blocking stains, or Ronseal Flexible Basecoat, which is designed to cover hairline cracks in one coat.
Whatever you use, the cracks usually come back after a number of weeks or months. The only way to stop this is to paper the ceiling with lining paper, which should contain the cracks even if they reappear. Bear in mind, though, that lining paper will eventually start to peel off.