Paint the Trim First, Then the Ceilings and Walls
Pros usually follow a certain order when painting a room. They paint the trim first, then the ceiling, then the walls. That's because it's easier (and faster) to tape off the trim than to tape off the walls. And you certainly don't want to tape them both off!
When painting the trim, you don't have to be neat. Just concentrate on getting a smooth finish on the wood. Don't worry if the trim paint gets slopped onto the walls. You'll cover it later when painting the walls. Once the trim is completely painted and dry (at least 24 hours), tape it off (using an 'easy release' painter's tape), then paint the ceiling, then the walls.
To Avoid Lap Marks...
To avoid lap marks, roll the full height of the wall and keep a wet edge. Lap marks are those ugly stripes caused by uneven layers of paint buildup. They occur when you roll over paint that's already partly dry. (In warm, dry conditions, latex paint can begin to stiffen in less than a minute!) The key to avoiding lap marks is to maintain a 'wet edge,' so each stroke of your roller overlaps the previous stroke before the paint can begin to dry.
To maintain a wet edge, paint an entire wall all at once. Start at one end, running the roller up and down the full height of the wall, moving over slightly with each stroke. Move backward where necessary to even out thick spots or runs. Don't let the roller become nearly dry; reload it often so that it's always at least half loaded. Keep the open side of the roller frame facing the area that's already painted. That puts less pressure on the open side of the roller, so you're less likely to leave paint ridges.
Clear the Entire Room Before Painting
If something is too big to take out, move it to the center of the room and cover it with plastic. Use canvas drop cloths. Unlike plastic, they stay put without tape and aren't slippery.
Avoid Drips as you Paint
Masking tape does a good job of protecting woodwork—if it's applied well.
Clean off all the dirt and grime along the edge of the trim with a damp rag. Hold the tape tight against the wall and roll it out so the tape covers the edge. Press the tape against the wood with a putty knife along the entire length. Use painter's tape that's at least twice as wide as the trim and leave it flared out to protect the face of the trim from drips. When you're done, either remove the tape immediately while the paint is still wet or wait until the next day when it's totally dry. If you pull it free when the paint is partially dry, you may peel off bits of fresh paint along with the tape.
Shine a Light Across the Woodwork and Circle Flaws
Position a hand-held bulb (at least 60 watts) so it shines across (rakes) the wood surface to detect loose paint, rough edges and other blemishes in the surface to determine what needs to be filled. Take a pencil and lightly circle spots that need work.
Consider Liquid Sandpaper, Especially on Lead Paint
After final sanding and vacuuming, some pros go the extra step of wiping woodwork down with a liquid sandpaper/deglosser (such as Wil-Bond by Wilson-Imperial or ESP by Flood). This step will ensure a good bond. And if you have to deal with lead paint, this step can replace sanding.
Dust and Vacuum Thoroughly
When the first sanding and scraping step is complete, dust off all areas with an old paint brush and vacuum woodwork with a brush attachment.
Fill all holes, even small ones
Run a Crisp Bead of Caulk Between Woodwork and Walls
Apply a thin bead of paintable acrylic latex caulk only inside the crack where wood meets a wall for a smooth, professional appearance. Remove extra caulk with a putty knife. And buy a dripless caulk gun to save time and frustration. Cut the tip smaller than you think you need.
Sand between coats
Take a Wool-Blend Roller Cover for a Spin
The most important part of your paint rolling setup is the roller cover, also known as a sleeve. It's tempting to buy the cheapest cover available and throw it away when you're done. But you won't mind the few extra minutes of cleanup time once you experience the difference a good roller cover makes. Cheap roller covers don't hold enough paint to do a good job. It'll take you four times as long to paint a room. And you'll likely end up with an inconsistent layer of paint, lap marks and built-up ridges of paint. Instead, buy a 1/2-in.-nap wool blend roller cover and give it a try. With proper care, this may be the last roller cover you'll ever buy.
Wool covers do have a few drawbacks, though. They tend to shed fibers when they're first used. To minimize shedding, wrap the new roller cover with masking tape and peel it off to remove loose fibers. Repeat this a few times. Wool covers also tend to become matted down if you apply too much pressure while painting. Rolling demands a light touch. No matter what roller cover you're using, always let the paint do the work. Keep the roller cover loaded with paint, and use only enough pressure to release and spread the paint. Pushing on the roller to squeeze out the last drop of paint will only cause problems.