We should be thorough of the subject which we are going to presentation. Present the presentation with confidence. If you forget any topic in the subject try to cover it with other topic with confidence but don't get stopped in the middle
Do you research well. Find as much as information and examples to the topic. Back your topic with relevant fact and figures. Always practice before you present. Make sure to speak loudly, slowly and confidently and if you are scared try and smile as much as possible. And the most important part,maintain eye contact.
first try to practice in alone than infront of your known persons and ask them about the faults if you have made and then after the complete practice go for the presentation.