Simple Future

Form: will VERB
I will call you tonight.
Negative Form: will not VERB or won't VERB
She won't tell you the answer unless you give her something.

Use 1: Use the simple future for spontaneous decisions (decide now without planning).
Do you want a ride home?
No, thanks. I'll walk home. It's such a nice day. (just decided to walk home)

Use 2: Use the simple future to make a prediction.
When we make guesses about what will happen, we use:
think...will               I think he'll be late as usual.
suppose...will        I suppose he will extend the deadline.
sure...will               I'm sure she'll need a new car.
bet...will                 I bet it won't work.
will probably         Fran will probably be a few minutes late.

When asking what someone thinks, we use: do you think...will
Do you think it will cost much?
How much do you think it will cost?
What do you think she will do when she finds out?
When do you think we will get their offer?
How do  you think Marcy will react when she sees the new color?

Use 3: Use the simple future to volunteer or promise to do something.
Bruce: Who will bring refreshments?
Andrew: I'll bring beer!
Ali: And I'll bake some cookies.

I'll call the doctor tomorrow. I promise.

For future plans, use the present progressive or "going to":
John is taking time off in August, and we're heading up to our cottage in Vermont. (use with already arranged future plans)
The nursing department is going to expand into a new building sometime. (use with intention of doing future plans)
Where are you going on vacation? We're not going anywhere. We don't have enough money this year. (use with already arranged future plans)