If you want to learn reiki, there are many different trainers offering courses. From CDs and DVDs to online courses, there have never been so many options available.
However, you have to wonder if you can truly learn reiki from a book or CD, or online. While these methods can be quick and convenient, and are certainly likely to be cheaper than a live course, given the nature of the skill, it seems hard to imagine that you can truly get a feel for it without actually experiencing it live.
The traditional way to learn reiki is through an initiation which 'attunes' you to the energy that flows through all of us. You first have to experience it, then practice it - at first on yourself, then eventually on others.
This self-treatment is an essential part of the process, and indeed, many people are quite content to use it only in this way, for personal development, improved health, and stress-management.
Thus this is not a skill that is learned in the usual way we are used to in the west. It does not depend on your memory or intellectual skills, simply on your ability to be attuned to the life force that flows through all of us.
There are three levels of knowledge - Level 1, Level 2, and Master. At each stage you become more attuned to the energy. To find a suitable course, contact your local complementary health centre, or check on the internet - look for courses that are highly recommended by others.