Generally, one can promote and sell his or her books personally or at events. Promoting or selling a book can be done nowadays in events like comic cons.
Trying to keep your costs down is the first thing to do in this kind of event especially if you are just starting, and you can do this by getting the most affordable table that you can find. Some can also share a table with another author if they are also interested in selling his or her books.
As an established author, ways of maximizing your sales can be done.
The number one thing you can do is to have a one-sentence pitch that summarizes up your book. It is best to not confuse people with your plot just in case it is an intricate one.
Next move is to make some noise. If you have an aggressive personality, like standing in front of your table and be able to hand the book to the passersby, and make some controversial or new message about the story, then do it.
Another way is to draw people with your irresistible offer, especially if you have a less sales-oriented personality, like pen, bookmarks, and others if you do not have a free print to give away. As you are giving away, it is best to stand since it is better to meet people are their eye level.
You next strategy is to have one book to push in order to get that sale. Note that the more items you are offering, the more distractions are challenging your buyers.
Upselling is another great idea, and you can do this by pushing one book and make an offer if they buy more than one or a bundle.
Another thing you can do is to promote your appearance at the event and have fun while getting many interests of your books. The event can also be used as your promotional activity where you can announce about your books to your fans, to media contacts and to potential fans of your work. Go ahead smile and have even if your sales have not yet reached your target or if foot traffic is low, because people have the tendency to buy from those who are smiling rather than those who are grumbling behind their desks.
During events like comic cons where the fun places are, people sometimes dress up as their favorite characters, and you can do this also to create interest of the book you are selling, and other means to get more attention except giving fright to passers by.