Your acceptance letter should clarify the expectations for your presentation. If it is not clear, you should immediately contact the conference organizers to inquire. You don't want to plan for a 75 minute lecture and then find out that you were expected to speak for 45 minutes and then respond to a Q&A session for 15 minutes. Conferences operate on a tight schedule, and you cannot overrun your allotted time. It's crucial that you don't speak for longer than you are scheduled to. However, it's okay to end a few minutes early. This is another item that should be made clear to you in the acceptance letter. You will need to know if you are presenting your paper to a large conference room as a keynote speaker, or if you are one of three presenters sharing a small space and time. If the acceptance letter does not answer any questions you may have, you should call the organizers and ask. Presentation formats may include conference panels, small workshops, large keynote addresses, round-table discussions, or general research reports. Review the conference website and study information about the sponsoring organization to understand the style that they expect. Many conference sites will include links to materials from prior years. These can be valuable sources of information as you prepare. Verify what technology will be available for your presentation. Do not assume that you will have access to wi-fi, for example, if you rely on Internet links as part of your presentation. If you are preparing a slide show, make sure that you are using a program (PowerPoint, Prezi, LaTex, Beamer, for example) that the host system will support. You must be thoroughly prepared to present your paper as clearly and professionally as possible, especially if you hope to be asked to return. You need to practice your presentation repeatedly. Whether you are standing at a podium reading your paper or presenting a more extemporaneous lecture using a slide show outline, you must appear polished and professional. Ask some trusted friends or colleagues to listen to your presentation and let you know if you are loud enough, slow enough, and can be understood.  Ensure your paper is written clearly so the audience can understand your points. Note that reading helps keep your audience engaged, while simply listening can make it more difficult for them to pay attention.

Summary:
Understand and meet time expectations. Know your presentation format. Familiarize yourself with the expected audience. Know your technology. Practice your presentation.