You should have a portfolio of your work other than the actual artwork that you will display at the art opening. A portfolio will add value to your entire work as people who come to you may express an interest in some of your other works. The Portfolio does not have to be big enough to cause you and others inconvenience.
Try to get a space where people can walk and stand freely. Art galleries are usually jam-packed at evening time and it can get very hard for people to appraise your work at closer quarters and make up their mind about buying it. If you already know the venue, try to book a space as quickly as possible, as you can demand your chosen spot.
Be approachable during the opening. The worst thing you can during the art opening is being unapproachable and extremely busy. Sound confident and give them impression that you are willing to listen to everyone and do not want to avoid interaction.
Usually, artists and exhibitors at art openings act like they are preoccupied and do not have time to talk to the attendees. Attendees will perhaps talks for minutes before making up their mind about buying your art work, so be prepared to entertain each of your visitors with care and attention.
Be interactive with the attendees. Visitors will want to know about your artwork at length. Most of the people who witness your work may be art lovers and know a lot about it. In this situation, you have to make sure you do not sound unprofessional. Be ready to answer a lot of questions and do your best to explain your work.
Do not spend too much time on one person, as it will turn off other interested parties.