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. Sharing a table with another author interested to sell his or her works is also another way.
As an established author, ways of maximizing your sales can be done.
The first pointer is to have a pitch that sums up your book in a one-sentence. 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. Standing in front your table is good if you have an aggressive personality, where then you can hand over your book to the people passing by and make comments of interest about your book.
Selling more of your books can be done by drawing more people in with some irresistible offer, and for those who are less sales-oriented person, giving away free print if you can afford, or simply give away pen, bookmarks and others would do. As you offer something for free, it is best that you are their eye level, standing and not sitting behind your table.
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.
To upsell is another idea to sell more books, and you can do this by offering a good amount for people buying more than one book or a bundle of the book that you are pushing.
By promoting your appearance at the event beforehand, you will have an increased visitors at your stand and at the same time have fun in the event. The time at the event can also be your promotional period, where you can talk about your book to your fans, to media people and to your potential fans. It is best to smile and have fun, whether sales are light and foot traffic is low, because people generally will buy from someone who is enthusiastic and not on the one who is grumbling behind his or her table.
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.