Well, I've had two so far. The first was a well-established reading series (weekly) here in Toronto. I read with two other novelists, and we were taken out for dinner prior to the reading.
The room was fairly small -- there were about 50 people, I guess? -- and set up with small tables. The room was lit by candles, except for the spotlight on the stage/podium (which, by the way, was stinking hot). I sat through two readings and an intermission before it was my turn, but I think I did well. Everyone told me so, in any case. I got some laughter and heard a gasp at one point. I read from the beginning.
My wardrobe is fairly limited; I wore a black top, a distressed jean skirt, and black boots.
My second event was a book club thing hosted by a liquor store here. Again, not the best timing on my (pregnant) part. Everyone came in (around 35 people), had a cocktail and a few glasses of wine, filled up their plates with wraps and salad, and then asked me questions for an hour or so. It was fantastic. I wasn't as nervous, for some reason, though this was more intense, obviously, than a 20-minute reading.