you don't want to have to explain marks from a spanking. Sex should be discussed...will it be part of the scene? If so, safer sex needs to be discussed? Roles should be discussed, whether or not they will be acted out. Even who is top and who is bottom, in some cases. Related activities should be discussed...will bondage be included? humiliation? Physical limits are an important discussion. Heart problems, back problems..those apply to both top and bottom! Does the bottom bruise easily, do they have breathing difficulty, any circulation problems? Emotional limits need to be discussed - was there any abuse or assault in the bottom's past? Any known triggers to prevent (or deliberately lead to) that catharsis we talked about?