As the homeowner, I've done all of our interior and most of our painting. Whenever you paint, preparation is truly key. Anyone can slap on a coat of paint and call it done. If you want something that looks good and lasts, take the time to clean the walls (also if there is a smoker in the house, nicotine sticks to paint), fill any holes, and take care of any imperfections in the surface. Also, tape off ceilings, door and window frames, and any other place you don't want paint to land. Depending on the size of the room and the number of doors and windows, it might take you 2-3 times the amount of time to prep as to paint. I've never had a contractor paint in my home, but if I did, the first question I'd ask is for a detailed list of how much preparation they would do. If it wouldn't be at least as thorough as mine, I wouldn't hire them. Also, ask about priming before painting, particularly if you're going to cover a darker color with a lighter one. There are now all in one primer/finish paints. If this is not going to be used, ask to have the primer tinted as close to the finish color as you can get.
The speed with which a painter can complete the job will determine its final cost, but time is difficult to estimate. Some painters have more experience and cover a wall faster, but some are more methodical and take more time. Most painters should be able to cover about 100 to 120 square feet of flat surface in an hour, unless they are working on a very large wall. Wood or plaster might reduce that amount to 80 to 100 square feet. You should also consider the time required for a first coat to dry before a second coat may be applied. This will add time as well -- anywhere from one to 48 hours depending on the paint.
Second coats on similar colors are almost never recogicnized as being needed until the coat is applied and has dried. ONLY THEN WILL YOU SEE WHETHER IT NEEDS A SECOND COAT or not. Yes, painters can use a cheaper paint then what you paid for. That is solved by getting your own which, I would charge extra for because I will always have to go get more, or add second coat because home owner tried to skimp on paint, or they got the wrong color etc...
Recently I had my kitchen cabinets painted with Warline. The workmanship is incredible. They were always on time, very considerate and managed all the details of my project with great care. During the entire process Heidi made me feel as though I were her only client and always made me feel at ease. I can't recommend Warline enough, and will be calling them every time I need painting.
To begin, move everything out of the room. Every painter we spoke with had a horror story about the time he didn't follow Rule No. 1. Bigger pieces of furniture can sometimes be left covered in the center of larger rooms, but if you are repairing drywall, says Chris Span, of Span's Quality Painting in Mobile, Alabama, "Take everything out. Drywall dust goes everywhere." Remove doors, light fixtures and hardware, and label everything with masking tape. Also, invest in drop cloths. "It's surprising how well a few drops of paint can cover a floor," says Rich Maceyunas, of Maceyunas Painting and Wallpaper in Waterbury, Connecticut. Buy high-quality drop cloths, such as canvas or paper-backed plastic. (Paint soaks right through lightweight fabrics and bedsheets.) Plastic sheeting works, but it's very slippery and doesn't absorb drips.
Most pros don't bother cleaning brushes and rollers if they are going to use them the next day on the same job. "Latex paint dries slowly in cold temperatures," says Maceyunas. For two-day jobs, he wraps the rollers and brushes in plastic grocery bags and sticks them in the refrigerator. "Just allow the roller to return to room temperature before reusing it," he says. Roller covers are almost impossible to clean thoroughly. Most pros buy new covers for each job.