However tempting it may seem, trying to save money by buying cheap brands of paint can actually work out more expensive in time, money and effort than buying a quality brand and making sure the surfaces are sealed and primed. Poorer quality paints tend not to cover as well so you'll need more - that's why they are often in such large cans - and you may have to paint two or three coats to get an even finish.
Make sure you have enough paint in the same colour and finish to complete the job. Paints are made in batches and there may be slight variations in colour between batches. It's better to have an unopened can of paint left over than to run out of paint halfway through and, in any case, most DIY stores will exchange unopened paint for other useful materials. When you have decided on your paint 'family' - water- or oil-based - and the finish - matt, silk or gloss - make sure you stick to it.
Start decorating at the ceiling and work your way downwards through the room, finishing with the wood-work. Clean up any drips as they
happen and remove any loose bristles as they fall out of the paintbrush. Always follow the manufacturer's instructions as some paints - except non-drip gloss and solid emulsions - may need stirring with a clean, flat stick before you apply them. Make sure your stirrer is clean so that old paint doesn't bleed into the new. Remember the professional painters' methods: decant paint into a paint kettle, and, if you are using old paint, pour it into the kettle through a piece of muslin or a clean, old nylon tight leg stretched over the neck of the can.