I would start out by writing a script which should include any details about the reality you plan to enter. Don't worry too much about forgetting to add something to your script as any blanks will be filled by your subconscious. The Raven Method is considered best for beginners, so I would recommend starting with that. If it doesn't work for you, that's okay! Usually people are not successful in their first attempt. Take a break, come back and you can try a different method if you'd like.
Also...about an hour before you go to bed something that really helped me was listening to a playlist that reminded me of my DR and doing light homework/reading (to feel like I was doing something for a class in Hogwarts lmao) and referring to myself in my head as whatever name I've chosen in my DR. It also helps me to sleep with a sleeping mask, and stay away from mirrors right before I shift because I don't want to see myself as I am, I want to try to imagine myself with the alterations I've made in my Dr (different age, different hair length, etc) also script what you smell like.