Be sure your slides or overheads are in the correct order. Rewind tapes or videos. Check the room temperature and be sure it is not too hot or too cold. If you are using handouts, be sure they are ready. Most professionals agree that it is best to give them out at the end of the talk so the audience listens to you rather than reads the handouts during your presentation.
Many speakers like to use a lectern because it is a handy place for notes, water and other items.
Some, however, consider it a barrier between the speaker and the audience. Some speakers stand beside the lectern, rather than behind it, in order to be more part of the group. If a lectern is used, it is important not to lean on it or slump down while giving the presentation. Remember that all speakers have nervous energy stored inside before beginning to speak. Channel this energy into strength and enthusiasm.