Over at Irish filmmaking blog Cigarrette Burn there’s a guest post from Liam Ryan, a 1st AD:

Essentially to me the job is logistics. For a given scene which might take place say at the Statue of Liberty involving character lighting a cigarette equal emphasis has to placed on the location or something that can pass for the location which might seem like a huge deal but you cannot forget the cigarette and lighter. Never assume that someone on the crew will have an item or that there is somewhere nearby where it can be procured. Chances are that it can be but what if the shop is closed, from the moment you arrive on location/ set you are on the clock and the less prepared you are the more time to you lose on the day. And something always goes wrong on the day so better be equipped to deal with that than have to also arrange something you could have taken care of at an earlier stage.

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As 1st AD I felt my primary job was to insulate the director as much as possible. From a directorial standpoint an instruction such as “Go for a close up on the actor as he lights the cigarette” can yield a lot of questions.

Cigarette Burn: Creative and Logistic – Thoughts of a 1st AD

Acting as a heat shield for the director isn’t all, you also have to be a cheerleader. One of Wes Anderson’s AD’s once told me that the best thing you can do is be smiling and into whatever the director is doing. I have too much pride to cross over to the side of obsequiousness, but a positive attitude on set goes a long way. Anyway, it’s almost inevitable that the cast and crew will resent the AD if he or she keeps them working. But the director and producers won’t, and that’s who the AD works for. It’s a tough gig, but a key one.