In order to be a Mystic, you need only to make yourself available and seek to experience God. These two conditions of genuine desire and personal availability are the conditions that provide for experiencing God. And, exciting enough, you can begin to experience God whenever you are ready. Even now!
So try it - right now. Find a quiet place - if possible. If not, where you are will do. Close your eyes - if you can. (If not, just sit still.). Slow your breathing and calm your body. Express, in your own way, your desire to spend time with God. (Even if it feels strange for now - please do it.). Remain quiet. Breath deeply and slowly. Let yourself feel. Start slow and increase the amount of time you enter into a quiet period.
That, in a simple way, is how anyone can experience God. It need not be complicated.
One word of caution. The experience will grow in its depth with repeated attempts. Also, length of the time spent does matter. A few moments will likely leave the participant wondering if anything has happened. Many mystics and teachers of the techniques encourage us to work our way up to around 20 minutes of availability at least once a day. Some may also put this together with verbal prayers or spiritual reading such as from Scriptures. The key is to be open to what you are experiencing. Also, what you will likely be feeling is Presence. Most Mystics do not have visions or get direct instructions. What they feel and share with the world is a deep connection with others and the world around them - and a deep and satisfying connection with our Eternal God!
This kind of connection changes lives! I know it did for the Saints and Mystics! I also know it has changed my life as well. It will also change yours - if you let it! Stay committed! Go all in!