I forgot one. Well, two, but one was addressed in comments. 

I came face to face with it in email a few minutes ago. And while I've successfully resisted the urge to do a direct email reply, I'll address it here.

Don't get pissy when you're asked to read the instructions you've already been provided. 

Seriously.  You have the information. You didn't bother to read it. twice.  Wait, no, multiple times.  I had to remind you that you are required to RSVP first, that you should not show up without a confirmation first, and that you hadn't indicated which workshops you would be attending.  In each case, the original email announcing these free workshops was included, which had the instructions and dates, which everyone else who has responded has read and followed.  A reminder that the information is in the original email should be a clue that perhaps you need to make the effort to read it.  A snarky reply is unwarranted.

The snarky reply will lose you the privilege of attending my workshops, at least until we have a discussion about manners and expectations.

I am not being paid by the organization to whose membership I'm offering these workshops.  I'm taking time out of my own job search to develop and run them, as well as schedule and setup the rooms, gather all the RSVPs and keep people informed, answer questions, as well as dealing with the commute time from the other side of town and back every time I give one.   I am not getting reimbursed or compensated in any way, shape or form.  I am doing this because I see a need, and a way to pay back an organization that has been supportive of me. 

So park the attitude.