Hi, Penny. Good question. There are 2 secrets to this. The first is to use an oil based primer and then a latex based paint. For subsequent repainting, use latex primer and paint and you will have to repaint about every 10 years, depending on your weather and local conditions.
The second is not to buy your paint at a home center and buy the best, most expensive paint you can get. Go to a specialty paint store that sells top quality paint like Sherwin-Williams or Benjamin Moore and plan to pay around $25/gallon. I know that you can buy the same brand cheaper at a home center but the paint companies make higher quality paint for theirown stores and price is usually more of an issue at a home center. But remember that if spending $10 more per gallon over the 4 gallons or so of paint and primer that it will take will give you 4 years or more life on the paint. That means that it is costing you $10 not to have to repaint for another year. That is sure worth it for me and you will get good local advise from the local paint store at no extra.