Know your audience and subject well, and plan your presentation. Practice your material aloud, and try running through your presentation in the location where you'll be speaking.
Practice in front of a mirror, or ask a friend or family member to give you feedback. You can also record yourself and watch the recording.
Make eye contact, smile, and use open body language. Ask questions and invite participation.
Speak slowly and clearly, pronounce words correctly, and avoid filler words like "um" and "like". Take pauses to allow the audience to process what you've said.
Try to embrace your nervous energy, and visualize success. You can also try deep breathing and relaxing before you present