So, first question first. What do you read?
This is a trick question. I don't know your work, so how could I make any specific recommendation? What I will do, however, is suggest a few things to think about in choosing a work to read (or read from).
- Consider whether you have a work that needs more visibility. Maybe you have something that has come out recently but from a smaller press or magazine which is more difficult to access; reading a work like this can increase the number of people who know about it.
- Consider whether you have a work that will be coming out soon. If you've sold a story and know it will be hitting shelves, or online sites, in relatively short order, it's good to relay this message to a potential audience and give them a bit of a teaser.
- Consider whether it is your best work. You might have a work in progress that is really exciting you at the moment, but be careful to consider that it may change a great deal in revision. Would you want people to hear the story as is if this piece of it may change dramatically later? Perhaps not, but you probably wouldn't want to read something that later you'd regret having shown in that form.
- Consider which part of your image as an author you are trying to project. I have two sides as an author: my science fiction side, and my fantasy side. I'm currently trying to grow my fantasy side so that I can be more three-dimensional as an author, so I chose at my local convention to read a fantasy story (currently under consideration by an editor) that I am very proud of.
- Consider what the overarching theme of the convention is. At WorldCon most of my programming was directly related to my status as an Analog writer and an expert on alien languages and language design, so it only made sense to choose a science fiction story to read. (I chose "Cold Words" because it will be coming out in anthology form soon.) It wouldn't make any sense to read science fiction at World Fantasy Convention, for example. And some reading slots specify the genre required, so it's best to go with that.
This might lead you to conclude that you should wish never to be scheduled on the last day of a convention. However, being scheduled on the first day isn't so great either - because you have virtually no time to drop your own name or invite people to attend.
I suggest a multi-pronged approach. Make sure you personally invite people you know who you know will be attending the convention. You can also issue public invitations through blogs or social networking sites, but it's hard to measure how effective these are. I don't suggest accosting random people in the halls and inviting them, unless you feel really comfortable talking to strangers. What I can suggest, though, is putting in a small plug for your reading at the end of panels you are on, just as the panel closes. Especially if the panel topic is related to the reading you will be giving, the chances of you finding interested parties in the panel audience is a lot higher. Thus I tend to mention my science fiction readings in alien language, linguistics or anthropology related panels. Worldbuilding panels are open to the suggestion of either fantasy or science fiction. Another approach that has been successful for me is to make up a flyer announcing your reading (with its location, the title of your story, and a blurb about its content) and post it up in public flyer areas of the convention, including near the door of the room where you will be reading. I made mine orange so it would stand out!
In the end, it doesn't matter if you're reading to two people or to thirty - give it your all. If you're a tepid reader because you've been put off by a small audience, those few members of the small audience will be unlikely to invite others to come back for a reading by you. Believe in the story, and give yourself to it. Make your story come alive, and then the reading itself can become a wonderful incentive for people to want to come back and hear you read again.
Note: special thanks to Lillian Csernica for teaching me so much about this topic!