Has the siding been painted before? If unpainted you need a stain sealing primer followed by top quality acrylic exterior paint. Top brands are Benjamin Moore, Kelley Moore, SW and others. You will get the best service and advice from a pro paint store. Ask for a preferred customer card for discounts. I strongly prefer to apply paints with a commercial quality airless sprayer, then back brush.

The only thing I will add to the previous post is that you want to use an acrylic solid hide stain as your finish coat as these products dry flatter and look more even on a textured surface and they hold up just as long as a regular house paint.