Use of the power of subconscious mind is known to be effective and has become quite common for manifestation and achievement of various goals. Some people learn from mind power teachers while some learn through books. Similarly interest in telepathy, hypnotism and meditation etc. is also on the increase. Reiki is also used to address various issues.
These are various tools that are used for different purposes with some overlap in certain sections. The point to understand is that every tool is not meant for everything. For example, hammer is not used to remove a screw and a screwdriver is not used to chop the vegetables. Similarly a person with a broken limb needs surgery not meditation. This is because every tool and system has its own functions and method of use. So have Reiki, meditation and other similar modalities.
Meditation is one that majority of folks tries to learn on its own using the information from Internet. There are plenty of methods available on Internet with impressive names but everything is not for everyone. A randomly picked up method might not always work because every meditation has a purpose and procedure. It is therefore, not advisable to pick any method and start meditating. Incorrect procedure is more likely to lead towards failure and waste of time rather than success. So is the case with use of power of subconscious mind. One can though learn it from books but that would be without guidance of a teacher and not very simple. One can make mistakes during the process and unwittingly make it counter productive.
Case with Reiki is quite different in the sense that it cannot be learned from books. Transfer of the healing ability requires attunement by a Reiki teacher where after it can be used anytime, anywhere without the fear of making a mistake. In fact there are no mistakes that could be made in using Reiki. This is a very great advantage of Reiki.
Having said all this, best option in my opinion, is to firstly decide what you want to do and then find a teacher of that modality and learn under guidance to eliminate the chances of failure or disappointment.