The most important aspect of a good aerial photo is to pick a day with good visibility and minimal haze. A conversation between the photographer and the client is exptremely important to get exact locations and acreage to be included in the photos. GPS coordinates of the property (if obtainable) are ideal. The photographer and the pilot need to work as a team, and both need to be knowledgeable of the assignment. A lot of pilots have taken photographers up in the past and are familiar with what angles and views make for good images. If the pilot is not familiar with flying for an aerial photographic shoot, it will make the job much more difficult. Also, the orientation of the buildings in the photographs is important to know so that the photographer and pilot know whether to go up in the morning or afternoon.
Avoid shooting through airplane windows as they will distort your photos when using a telephoto lens. I use a very fast lens (usually f/2.8) with image stabilization and a professional high-resolution digital SLR camera.
The most important part of aerial photography, however, is a good conversation of expectations with the client. Understanding the exact angles and views that the client wants is always the number one priority before going up in the air.