I've read, and heard, many times that the gist of a talk's structure is:

tell 'em what you're going to tell 'em
[stuff you came to tell 'em]
tell 'em what you told 'em
thank 'em and say goodbye

I've experimented with this and have found it's definitely a good go-to formula, especially if you're just starting out.
I do think there's a little more to those last two bullet points, though. Summarize a talk by recapping, yes. Good stuff. Gratitude - a MUST. I believe there's also got to be something between those last two bullets in a speaker's tone or message that sends the audience off with a really great feeling. If I've taught them something, I try to remind them why what I've shared is useful, or how it can improve their life. If I've shared a personal story, I aim to share the positive outcome not only through your message but also through your voice and energy.

"I've learned that people will forget what you said, people will forget what you did, but people will never forget how you made them feel." -Maya Angelou

Think about how you want your audience to feel.

Seal the deal on why your talk was worth their time. Then thank them and say goodbye.