Spend money to save money. Experts say a top-quality exterior paint can save you money in the long run over cheap paint. This is because premium paint generally lasts several times longer, and you'll have to repaint less frequently. That said, you don't need to spend $70 per gallon or more; many top-rated exterior paints range in price from $30 to $40 per gallon and perform just as well as or better than the priciest options. Even in the short run, spending a few dollars more for a quality paint usually does the trick in just one or two coats, experts say, while you may need more coats of cheap paint to get the same coverage.
Match the color you want, or buy some samples. Many paints can be tinted in nearly infinite variations of colors. If you want to match your existing color, bring a sample of the paint, or a paint chip, to the store. Paint sellers have equipment that tells them which colors to blend to make an exact color match, and the service is usually free. If you're uncertain about which color you want, or whether or not it'll look good on your house, buy a sample. Many retailers sell small pre-mixed containers of paint, so you can see how well a paint looks when dry before buying larger quantities.
Match the existing type of paint. While latex (acrylic) paints are preferred over oil (alkyd) paints in general, experts recommend matching the existing type of paint if you're repainting a surface. Use latex paints on existing latex finishes, and use oil paints on existing oil finishes. This is because if you're painting over many layers of old oil paint, a new coat of latex can actually cause the old oil paint to peel off in sheets, because the two paints react differently to moisture.
Consider a wood stain for decks. Deck stains are ideal for when you want to show the wood grain of a deck or porch. Clear (or transparent) stains accentuate the wood grain the best, but are the least durable. Solid stains are the most durable because they're the most penetrating, though they hide the wood grain the most.
Proper prep matters. Regardless of the quality of the paint or the skill of the painter, failing to properly prepare surfaces for painting will doom the job to failure. Surfaces need to be clean and dry and any loose paint needs to be scraped away. You'll also want to repair any damaged surfaces. FamilyHandyman.com has a primer on the steps to take to do the job right.