There are some yoga basics that should be focused on for most postures. It is useful to know and to understand the benefits of these aspects because they will help you progress and feel better during and after a daily practice. In yoga, one of the physical goals is to create space in the body. This means to expand and lengthen, as opposed to compress or collapse. So we try to get longer and to open up the body.
This is probably the most important yoga basic. Of course, your body will know that it has to breathe. However, you might find difficult to breathe at a normal pace while in postures that are challenging for you. Sometimes, the required strength for a pose will be demanding enough for you to be out of breath. At other times, you will find a pose to be relaxing and easy. Either way, I recommend that you use Ujjayi Breathing during your practice. This is a slow and deep breathing technique that will fill your body with energy and, at the same time, is calming for both the body and the mind. Start to practice it right away. By starting early to do it, you will create a habit of doing it and soon it will become natural during your yoga practice.
Until it becomes natural, though, you might forget. While learning the asanas (postures), your mind is likely to be focused on all of the different aspects of the postures, and not on breathing deeply. So it is easy and normal to forget. As soon as you realize it, simply come back to it.
To lengthen the spine is another important yoga basic. Lengthening the spine creates space between the vertebras and helps relieve the discs from the pressure that they get from gravity. Lengthening is good for the body's posture, it helps release tensions and, most of all, it will make you feel good. So remind yourself to reach with your head, away from your sacrum and avoid compressing the vertebras as would happen when dropping the head back. Instead, use your strength to support yourself and feel the stretch in the muscles.
Again, create space. This yoga basic will help free up your neck. Roll the shoulders back and down. The shoulder blades should follow this downward movement. It might feel awkward in some postures, at first, to keep the shoulders down. In Warrior I, for example, the hands are up toward the ceiling. Having the shoulders down might feel awkward. But feel the space that it creates for your neck. After some practice, doing it should become natural and more comfortable.
Your feet are your foundation. They take you everywhere you walk, they allow you to stand up and they are what your body bears on. In yoga, when practicing standing postures, try having a good contact with the ground. Feel all four corners of your feet touch the ground, as much as possible to get a good foundation. Have a good base for the upper body to rest on.
Spread the fingers and reach through them. We tend to let the hands be wherever they end-up and forget about them. Instead, keep them active. This will create an increase of the blood flow in your arms, hands and fingers. Allow this energy to flow all the way through your fingertips.
The hands should be kept active during hand bearing postures also. For example, in Downward Facing Dog, spread the fingers and reach through them, pressing them down to the floor. This will help support your wrist and avoid injury.
All of the above yoga basics will come with time and practice. At this moment, maybe it sounds overwhelming. Don't let this stop you from learning and practicing yoga. Take it one step at the time as you progress. It is ok and normal not to remember everything when you start. As long as you put some effort in your practice, you will gain benefits out of it.