I recently posted a reply on Fetlife to a request regarding first time visits to Nimhneach, the monthly scene club night in Dublin. I felt that my status as only one extra visit removed from novice qualified me. For the benefit of any readers here, I repeat the post below.
I would endorse the suggestion of going to the meet & greet. We have only been twice, but we met up with the M&G organiser beforehand each time. If its who it was for us, you can't help but be relaxed. OK, even though it is vanilla dress, you can tell whose waiting to be met because they're lurking near the door, scanning every new entrant and, in our case, getting ready to bolt, and they're all carrying sports or shoulder bags like a dispossessed football team, but are otherwise in street clothes. There are changing facilities at Nimhneach, and a cloakroom within the venue (who are sympathetic to you retrieving your bag to add/remove items). Most people use those facilities.
Just one thing to be prepared for, the changing facilities are unisex (in the hairdressing sense), but you won't show or see anything that you're not going to show or see at Nimh anyway. You can always use one of the loos next door if your shy or want to make a grand entrance. Those facilities are all within the Nimh area and are not overseen by other venue attendees.
From our limited experience (two visits) I would say that Nimhneach is really cool, relaxed, inclusive. and respectful. From the meet & greet you go in a group, so at the ticket desk you can just say "the same again" and follow the previous person down the stairs. If you're carrying a shoulder bag with your gear, the much threatened security staff are happy and no, they don't ask you to spread it all out on a table like airport security.
Be brave and take the plunge,its only scary in a nice way.