The material of your presentation should be concise, to the point and tell an interesting story. In addition to the obvious things like content and visual aids, the following are just as important as the audience will be subconsciously taking them in:
Your voice - how you say it is as important as what you say
Body language - a subject in its own right and something about which much has been written and said. In essence, your body movements express what your attitudes and thoughts really are. You might like to check out this web page
Appearance - first impressions influence the audience's attitudes to you. Dress appropriately for the occasion.