“So, I'd like to introduce our first speaker, Tom Johnson.”

You are the organizer of a conference. You are introducing the first speaker. You start by saying "thank you" to the audience for coming. You say this when you're ready for the speaker to begin.

So, I'd like to introduce our first speaker, Tom Johnson.

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So, (sentence)

This is a good way to signal a new "part" of a conversation.

For example, when you're starting a meeting, you can start by welcoming everyone and sharing general information. Then, when you're ready to talk about the main point of the meeting, you can use "So":

So, let's talk about our budget.

You can use "So" to switch to a more serious topic when talking with friends or family:

So, how are things going between you and Kelli?

You can also use "So" to transition between describing a problem and talking about the solution:

...and now we're losing over $200,000 per month. So, obviously, we need to talk about cutting costs.

I'd like to (do something)

You say "I'd like to ___" to let the listener know what your purpose is. For example:

I'd like to introduce our first speaker.

You say this before you introduce him.

I'd like to place an order for delivery.

You say this when you call to order food to be delivered from a restaurant.

You use the phrase "I'd like to (do something)" this way mostly in speeches, or when you're talking with someone like a bank teller or a restaurant host. You don't often use it in face-to-face conversation between people.

introduce (someone)

When you "introduce" a person, you tell listeners who this person is.