OK

You can use "OK" before you ask people to make a decision. When you start with "OK", it prepares the listeners to pay attention to the question. For example:

OK, let's decide where we're going. James, what do you think?

OK, who's going to ride with me?

who wants (something)

Ask "who wants ___?" when you're asking a big group and just want to see the number of people who want something. You can also ask other questions to a group in this way:

Who here has been to Seoul?

Who needs a ride?

Here are two good responses to this question:

I do!

Me!

In larger groups, the way to respond to this question is to raise your hand.