Even the most seasoned speakers can get nervous prior to presenting. The most effective way to take the pressure off of you is to change your mindset and think about serving your audience, rather than focusing on your performance.
Remember that you are there to provide your listeners with valuable information that helps them. If your audience leaves with even one or two new pieces of information or a new perspective, you have made it worth their while. By focusing on being helpful or in service of the audience, you will be able to relax.
Also chatting with the people that you are going to be speaking to before you give your speech can help you serve your audience even better. Not only does it warm them up to you, it lets you gauge their sense of humor, which is particularly critical if you are a speaker that tends to let a curse word fly or uses bold and provocative stories or language.
Moreover, you can glean insights to incorporate into your presentation. It's incredibly effective to use audience members as examples or transitions in a speech, because it creates intimacy with the audience and more engagement.
If you are talking to small-business owners about marketing and Susan, for example, told you a great story about how she used an unusual marketing tactic, incorporate Susan and her story into your presentation. "Speaking of clever marketing, earlier I was talking to Susan, who is sitting in the third row, and she told me how she used a PR stunt with 400 kittens to get new clients…"