I am in a study seminar with my advisor. By the nature of the seminar, sometimes we have to go into details of hard proofs instead of waving our hands like in an ordinary seminar.

My question is: How should one determine the amount of detail of a proof to be included in this kind of situation? Is there any type of proof that just should not be presented? (e.g proof that is only bookkeeping or dull homological algebra)