A tad clickbaity, perhaps, but here's something that worked for me. For 1 week, every day you'll listen to shamanic drumming (make sure you put your headphones on). Here's a track that I absolutely recommend (best one out there in my humble opinion): https://www.youtube.com/watch?v=DgD1oruX6WE
Relax and let the beats take you into a trance. Don't try to force it. Once you're in an altered state of consciousness / trance, perform a hand gesture or do something with your fingers (anything you want) and while you're doing the gesture, affirm to yourself: "this puts me in a trance" or "this puts me in this state."
Do this for 1 week, and your subconscious mind will associate the gesture with the trance state, thus the gesture will become a trigger for the trance. Once the association is made, you won't need the drumming anymore. The gesture will be enough to alter your consciousness within seconds.
Note: for some of you it might take less or more days to establish the association, but generally 1 week should be good.