Getting that precise, straight line on edges of a wall or where the wall meets ceiling is one of the hardest parts of painting. It's even worse if you have textured walls or ceilings. The Make It & Love It blog reveals this "pro painter's secret" to sharp lines perfection.
Actually, Ashley posts two methods. The first, her preferred method, is one we've mentioned before. It's the error-free method of painting a ceiling and wall or two walls different colours. Tape the edges where the two walls (or wall and ceiling connect), then paint the first wall right over the tape and into the other (still unpainted) wall and let it dry. The dried paint prevents the other paint from seeping under the tape.
The second method is useful if your ceiling or other wall is already painted and you just want to paint one wall. Tape the edges, but also apply a line of paintable caulk into the edge of the tape. Smooth the caulk out with your finger, paint over the caulk and tape and pull off the tape before the caulk tries.
The results will look quite professional. Hit up the link below for full directions and photos.