Well folks it's that time of the year again.  Time to paint.  Here are a few tips on successful exterior painting that will help reduce the need to repaint so often.

If starting a new project, select your woods carefully.   Paint just sticks better to some woods than it does to others.   Softwoods with narrow bands of summerwood (the darker portions of the grain) and fine grained hardwoods hold paint best.   Spruce, Poplar and White Cedar are all good choices.

The key is preparation.   Paint doesn't stick well to the burnished surface of most milled lumber.   Sand with 120 grit paper to give the wood some tooth, and remove surface impurities.   No need to sand finer... a glassy smooth surface defeats the purpose of sanding in this case .  Fill cracks and checks with a quality, non-shrinking wood filler before sanding.

Apply an alkyd (oil based) primer.   Prime ALL exposed surfaces, don't forget parts that will touch the ground.   Allow to dry completely and sand lightly to improve paint adhesion.

Follow with two, light coats of a quality exterior paint -- latex or oil based.   Gloping on thick coats will only cause the paint to crack, keep them thin.   Add another coat if you feel the need for more protection.  Ideally, the dried layers of paint will be about as thick as a sheet of paper.  Let each coat dry completely before applying another.

That's all there is to it.   With careful preparation and quality materials you shouldn't have to paint more than once every 3 years, depending on your location.