As already mentioned, the Iyengar method is very precise and lays great emphasis both on details and on the body’s alignment.
You can generally check the latter simply by looking at yourself – for example, at the line of your feet in a standing pose.
The front foot should be turned out 90°, the back foot turned in at a smaller angle; the front foot should be in line with the instep of the back foot. In this way you will achieve a secure, stable stance.
You will get a better feeling for the alignment by looking closely at the photos.
Once you are familiar with the poses, you can enter them more quickly.
You will then have more opportunity to check your final position against the instructions and you can stay in the poses longer (and thus practice more intensively).