High quality video. Pass through without any toys (better on Quest 3). Hypnotic/trance music or beats in the background -- also self hypnosis. Also, practicing with hands free orgasm audio sessions when not using VR.
One technique that works really well for me results from having very strong Kegel muscles after years of doing Kegel exercises. Without touching myself, I clench and unclench the muscles in my groin in sync with the action in the video. After doing this for many years now, it is automatic. I have to make a conscious effort to stop this from happening. But I will say that the results are worth the effort because it is amazing to add to immersion.
Then there are drugs, both legal and illegal (depending on where you live). If used wisely, they can turn your VR experience into Sex Like Real! Viagra keeps you hard if you do not want to use your hands. The harder I am, the more it seems to add to immersion. Adderall seems to heighten immersion. Weed, molly, MDMA, and psilocybin (magic mushrooms) can all add to immersion. Sometimes they work great together. But be careful and don't overdo the doses, first, because you could get very sick or even die, and second, some of those substances make it very difficult to maintain an erection and/or to have an orgasm.
Hope this helps people have more fun!