Mutual agreement is mandatory. S&M needs trust. Take alarm signals seriously! The sub (also slave, submissive partner) can withdraw his agreement at any time. Agree in advance on a signal (word or gesture) that will clearly end the session (“No” is often unsuitable here, agree something else). Inform yourself as a beginner about possible risks. Alcohol and drugs can affect the realistic assessment of the situation and your limits.
Get tested for HIV, Hep C and other sexually transmitted infections (STIs) at least once a year. Swabbing your dick, ass, and throat is a sure way to find anything that doesn’t belong there. Vaccination can protect you against hepatitis A and B.