There are several very important steps that you must take in order to become a reiki master and I can only mention a few of the most basic ones here. Because the difference between temporal matter energy and spiritual matter energy is that the former is more course and the latter is more fine, yet they are both manifestations of energy. This requires the serious Reiki student to cleanse their inner vessel, both temporally, as well as spiritually, before beginning a serious training of Reiki. Our temporal bodies are electrical energy receptors and conduits for that chi or ki energy which we use in Reiki healings.
This means that in order to become a reiki master who can affect a great change, both the temporal body and the spiritual body must be cleared of all blockages. If this means going on a mucousless diet with no processed substances entering your physical body, and staying in meditation for a few months to cleanse your spiritual body, then so be it. You cannot be an effective receptor or conduit for the chi or ki energy that heals, when your physical body or your spiritual body is all clogged up and full of blocks to the flow of the ki energy.
Another step that must be taken in order to become a reiki master, is that you should most definitely wean yourself away from mental images which will certainly prove diversions to your path. It will require sacrifice of unrealistic images from the many differing technological sources that bombard our minds each day, in our so called advanced civilization. You will be much more effective as a Reiki healer if you purify your mind and thought patterns. By spending time reading uplifting books and going outside to feel the ki in the beings of nature, such as the trees, the plant and animal life, you will find yourself accessing greater ki power. Many native spiritual societies also know this to be true.
And one final word of advice to become a reiki master, is that you humble yourself enough to "unlearn what you have learned", in order to be open to new truths that will inevitably fit with the previous truths, of which you became familiar. There should be no fear in letting go of your paradigm or mind set long enough to make room for the additional truths that Reiki will allow you to discover. This is because all truth is independent in the sphere in which the divine has placed it, so you need not worry about losing previous truth, in order to make room for the new.