I would agreed with Zakyrus but there are different ways to cook a potato an old friend told me once.
Old school for opening the third eye was to perform breathing into the lower Dandien and raise the energy up to a very high level-which usually took years. Sometimes controlled or mostly not being controlled it would work it's way up the spine to and fill the Upper Dandien. Usually you had a Master to guide you as the moving of energy up the spine, without guidance can allow it to go off in many directions and cause many problems. If the student suffers from 'Monkey Mind' then it would be very difficult to accomplish filling the Upper Dandien without a Master. Monkey Mind is like Spiritual ADD. Once the Upper Dandien is filled you become aware of the Third Eye and next send energy to it to encourage it to open. This may still take years and can cause many physical or mental problems if done incorrectly, because of the higher level of energy and the energy centers not being balanced. It's still a slow process. The pay off is usually worth all the effort put into it.
The new school is much safer. Enter Small Universe Breathing and you slowly raise your energy level in a much more balanced and practical method. All the applicable energy centers are raised at the same time and it is much more comfortable. The 3rd eye opens slowly and you are aware that something wonderful is happening.
The last part is being with a Master who can also enhance your energy and help to open your 3rd eye as Master Lin does. Normally known by "Transmission". Few people ever make these levels without a gift from a Master whom has been there and done that. Remember their third eye is open and they can usually see right through you if they choose to, but is mostly reserved for those special Student/Teacher moments. Traditionally they only look deeply into someone who may demonstrate something-usually by accident.
In this process, having appreciation, giving thanks to those on your journey and being kind to yourself makes it much more enjoyable.