The first thing you need to look at is the space you want to cover versus the size of the awning and the overhead area that you have available to install it. Many people discount overhead space as a minor consideration, and it generally is not a deal breaker, but it can have a large impact on how much pitch your awning will have. When people in the awning industry say awning pitch, they mean how many inches does the awning slope down for every 12 inches that it extends from the supporting structure. There are industry standard recommendations, but those vary quite a bit by brand, manufacturer, and size. The main point to keep in mind with awning pitch is that the main purpose is to keep water rolling down and off the material when it rains. If water pools up it will quickly stress joints, stretch fabrics, and possibly cause the awning to rip or collapse. You want water to flow off the top or side of your awning quickly.

The higher the overhead space that you have for installation, the greater the pitch your awning can have when fully extended, and the greater the height between the roll and the ground. This is significant because people will actually be walking underneath this. Seven feet is generally considered to be acceptable since the average person is well below that height, but if you have special considerations you must take those into account. And, the longer the awning (as in, the further out from the structure it extends), the more room you need to maintain an acceptable pitch.

The next important aspect is the material of the supporting structure. House exteriors come in all different types of finishes, from vinyl siding to cedar shakes to stucco. All these different finishes require different considerations for installations. Different manufacturers have different mounting styles, but generally you'll have to install several brackets for supports and the awning fabric retainer, plus some sort of track along the top. These brackets need to be flush with the supporting structure so vinyl siding may need to be cut and shims or blocks put in place to keep the hardware proud of the finish surface.

The last thing to keep in mind is that retractable awnings weigh a considerable amount, so you need to make sure that they're attached to studding or some other solid base. They absolutely cannot be attached with any type of expanding anchors, and I would certainly recommend having a professional perform the installation if you have block or brick exterior.