Don't use any tape on the walls. Chances are, no matter how recent they have been plastered/painted, you will pull some of the surface off when you remove the tape. If you're using a matt emulsion, roll/brush the walls before 'cutting in'. If silk, do the 'cutting in' first.
For the 'cutting in' make sure you have a good quality brush - angled ones are superb - load it with paint and begin cutting in about 1/2 inch below the ceiling. Slowly drag the brush, and it's reservoir of paint, up to the ceiling and paint a straight line until your brush begins to run dry. Then, reload the brush, begin about 6 inches away from where you ended, and drag the brush in the opposite direction until it has overlapped your first application. Remove any extra build up of paint with your brush. Continue this procedure until you have cut in around the room. Tape the skirting boards up, ensuring that there is no tape on the wall, and cut in along the bottom of the walls. Then cut in down the corner angles either side of your feature wall - no need to be neat on the walls that do not meet the feature walls. Tried to make that sound as simple as i could; hope i succeeded.