Skipping Prep Work
You've chosen your colors and have the paint ready to go. You're all ready to paint right? Wrong!. Prepping the area to be painted is one of the MOST important steps to completing a successful paint job. Any surface defects need to be sanded down. Any areas that are dirty or stained and are not cleaned properly can cause poor adherence and crack and blister the top coat of paint. Making sure the walls or area to be painted is completely free of dust, dirt and contaminates will ultimately make or break the final appearance of paint.
Not Buying Enough Paint
Nothing is worse than getting near the end of a job and realizing there isn't enough paint left to finish that last wall. Not only does it mean more effort to run to the store to buy another gallon, but a lot of the time the color of the new paint will be slightly off from the original paint. Making sure you buy enough paint from the get go will save time in the long run, and if you need to touch up any areas later you have the paint ready to go.
Over-Brushing the Paint
For the smoothest finish it is imperative that you don't over-brush the area being painted (especially trim). Over-brushing can leave drag marks and you'll ultimately have a ridge-like surface. Nobody wants that. Here's how to avoid over-brushing. Load the brush (dip the brush in 1/2 - 2/3 of the way up the bristles, then quickly cover the area with paint. Now take a stroke or two to level it out and stop. Brushing once the paint has begun to set up and dry can tear the initial film causing bumpy areas that will need sanding to fix.
Forgetting to Put the Lid On
Here's the issue. Paint is made to dry when exposed to air. This starts happening the second you remove the lid. I know, you're all thinking this is a no brainer. However, when painting it is usually the last thing most people think of. Either you are too busy trying to get the job done or you think you'll be using more paint shortly so why spend the time putting the lid back on. The fact is even in a short period of time dried paint can accumulate in the can or on the lid. Now, you put the lid back on once you're done painting and you've got the perfect conditions for that dried paint to make its way into the good paint. Next time you use it you may notice chunks or skins sticking to your roller or brush causing uneven coverage or drag lines.
Not Sanding Before Painting A High Gloss Surface
Higher gloss paints are great for heavy traffic areas but you can't just paint over a glossy surfaces and here's the reason why. High gloss paint is glossy because at a microscopic level the surface is extremely smooth. This smooth surface is what gives high gloss paints its ability to be easily cleaned as there aren't surface defects that dirt can adhere to. But, that is also what makes it hard to repaint a glossy surface. A fresh coat of paint needs something to stick to and by lightly sanding a glossy surface you give it enough texture for the new paint to adhere.
Applying A Second Coat Too Quickly
Now I get it, you want to complete your painting job as quickly as possible but that doesn't mean you can just cut corners without repercussions. Not allowing the first coat of paint to dry completely can, and in most cases will cause the first coat to peel and tear. Giving the first coat proper time to dry is a must and if you can't find the recommended dry times on the paint label a good rule of thumb is 24 hours between coats.
Painting A Dimly Lit Area
Always make sure to have adequate lighting in any area you are painting. When painting in a dimly lit room for example, it can be hard to determine whether you are achieving proper coverage or not. As far as you can tell the room looks great, but open a window or door and all of a sudden the areas you missed become glaringly obvious. This is easily avoided by keeping window blinds open or setting up a lamp so you can see exactly what you are doing.
Rolling In One Direction
Ok, this one happens a lot. You've rolled out the wall and its looking good. Then you get a closer look and notice that there are some nooks and crannies that haven't been properly coated. To ensure a uniform finish it is necessary to work the brush or roller back and forth in what we call an 'N' pattern and it's exactly as it sounds. This helps the paint get worked into the spots a standard 'up and down' motion just wont get to. Also keep in mind that you need to make sure to work in sections and always keep a 'wet-edge', meaning don't allow the outside of the painted edge to dry otherwise you'll end up with lap marks that will be visible once the paint dries complete.
Painting New Drywall?
There's A Primer For That
New drywall is extremely porous and will assuredly soak up an excess of paint before it is properly sealed to allow for the top coat of paint. Drywall sealers are less expensive than painting the wall with the paint you've already selected for the top coat. Not to mention drywall sealers are formulated to penetrate into the drywall and prevent 'flashing', a term in which areas of the wall are shinier or duller than the rest due to the paint soaking into the wall instead of being held out on the surface. Why not save money while achieving the best performance? It just makes sense.