Communication is essential, without it no-one gets what they want/need. Negotiation shouldn't be part of the 'chase' because the discussion needs both parties to have personal authority, it's where 2 people find out if their kinks mesh well enough for a scene or not. The tone shouldn't be set until the boundaries are in place.
As part of a lifestyle, the structures tend to evolve with time and limits will be reviewed - what you are comfortable trying with a partner you've known for 3 years may be very different to what you will try with a partner of 3 months. When a safe word or caution word (safe word stops everything, caution word means slow down because something wrong) is used, there should always be a frank discussion of what happened, what went wrong, does there need to be a boundary in place etc.
When you're talking about a scene, it depends on familiarity, relationship, potential for relationship. Setting boundaries and discussing safe words/limits are things which might be established between 2 people who play regularly so a pre scene 'negotiation' might not be detailed - the discussion afterwards may well be more important (what was good/bad/scary/exciting/intriguing). With a partner you've never played with before, the negotiation is vital...and so is keeping the D/s dynamic out of it.
Dom(me)s beware though, if you are a member of a (reputable) club you will earn a reputation and be judged by it.