Safe words are covered on the Playfulness page. In addition to verbal safe words, non-verbal safe queues should be established in case of gag or other verbal impairment (such as choking). Consent is covered in Advanced Topics. Consent is foundational to kinky play, especially in the BDSM community, but has a lot of nuances that should be discussed before play sessions.
Non-DS: A
DS: During DS sessions the majority of verbal communication will likely be commands.
Adequate time should be allowed after a session to allow for mutual reflection and the discussion of any problems or concerns. Establishing this space may prevent in-session issues from needing to be addressed urgently.