I'm starving!

The word "starving" technically means that you haven't eaten for days or weeks and your body is in pain from not having enough food. But when people are hungry, they often exaggerate their hunger by saying "I'm starving!"

Saying "I'm starving" when you're hungry is casual but can be used in business situations as well as with friends. It's a little more common for men to say than women.

Let's (do something).

The phrase "Let's ___" is well-know to English learners. However, learners often over-use "Let's ___" and use it in situations where it isn't appropriate.

When can you say "Let's ___"? You usually use it when you're suggesting something that you're sure the listener will accept. In the example above, you're meeting your friend for lunch, so of course she will agree that it's a good idea to eat.

In situations where you're not sure how the listener will respond to your suggestion, you can use other phrases like "Would you like to ___?", "Why don't we ___?" or "We should ___":

Would you like to go out to dinner with me some time?

Why don't we meet at 7:30?

We should get together some time and have a drink.