If you're an entrepreneur, do you go out and speak in your community because you want to build your business? Of course you do! It's one of the best (and least expensive) ways to get the word out about your product or service.
But be careful... If your only goal is to get clients and make money, you might not be as successful as you would like to be.
Public speaking is a service. Your audience wants to know what's in it for them; that is, what is it about your product or service that will benefit them? You provide education, information, and entertainment to your audience. In return, they might tell their friends about you, interview you for the local paper, ask you to speak at another event, sign up for your mailing list, suggest possible partnerships, and -- oh yeah -- they might buy what you're selling.
Think of your speaking engagement as a networking opportunity. Instead of focusing on what you can get, think about what you can give. Realize that "success" might look completely different from what you're imagining. Realize that "results" might come two years down the line.
Results and success will come. Don't try to force it, rush it, or grab it. Don't think of your audience as a meal ticket and expect them to start throwing money at you.
Be a giver; make your presentation a gift to the audience. Think about their needs and desires first, and you will be rewarded, in one way or another.