There's more to painting than just slapping the color on the wall. Like most things, a certain technique is involved. First, start your exterior paint job from the top of the house and work your way down (it's harder to drip up, after all).
If you're using a brush, dip about 2 inches (5 centimeters) of bristles into the can and shake off the excess by slapping the brush against the sides of the container. Lay the paint on thick, quickly going back and forth about two or three times. Reload your paint and repeat until you've covered about 3 or 4 square feet (0.3 to 0.4 square meters). Finally, smooth out your work with your brush (this time, without adding any extra paint). Use long strokes and work from the unpainted area to the painted area [source: The Family Handyman].
For rollers, dip your roller into a 5-gallon (19-liter) bucket and shake the excess off on a roller screen, a metal grid that can hang in the bucket. Using moderate pressure, roll the paint on to your surface, reloading when the paint no longer flows easily. Cover 3 to 4 square feet. Follow up with your brush and paint in the crevices and siding [source: The Family Handyman].
If you're painting overlapping siding, paint the "butt" or bottom edge before working on the broad surface [source: Truini]. To minimize lap marks, paint a section of four or five boards all the way across before the paint has a chance to dry [source: Benjamin Moore].