WAYS OF EXPRESSING THE FUTURE

For plans and arrangements:

I´m doing something tomorrow. - I´ve arranged, I´ve planned to do it.
I´m going to a concert tomorrow.
Alice is going to the dentist on Friday. (She has an appointment)
We are having a party next weekend. (Everything has already been planned.)

Decision, intention to to something:

I´m going to do something. - I´ve decided to do it, my intention is to do it.
I´m going to buy some new books tomorrow.
Sarah is going to sell her car.
I´m not going to have breakfast this morning. I´m not hungry.

Something is going to happen; it´s clear now that it´s sure to happen:

Look at the sky! It´s going to rain!

will/shall - Simple future

Sue travels a lot. Today she´s in Madrid. Tomorrow she´ll be in Rome. Next week she´ll be in Tokyo.
You can phone me this evening. I´ll be at home.
We will probably go out tonight.
I won´t be here tomorrow.

Don´t drink coffee before you go to bed. You won´t sleep.
I think I will pass the exam.
I don´t think it will rain this afternoon.
Do you think the exam will be difficult?

Also used when you offer or decide to do something:

'My bag is very heavy.' - 'I´ll carry it for you.'
'Bye! I´ll phone you tomorow!'
(the phone rings) - 'I´ll answer it!'

Shall (you can say 'I shall' (= I will) and 'we shall' (= we will)

Do not use shall with you/they/he/she/it:
Tom will be late.


Shall I/we...? = Do you think this is a good thing to do? Do you think this is a good idea?
It´s warm in the room. Shall I open the window?
I´m going to a party tonight. What shall I wear?
It´s a nice day. Shall we go for a walk?
Where shall we go for our holidays this year?

Present Simple with a future meaning: we use the present simple when we talk about timetable, programmes, etc... (e.g. for public transport, cinema, etc...)
The train leaves Plymouth at 11:30 and arrives in London at 12:45.
What time does the film begin?
It´s Wednesday tomorrow.

We can use the present simple for people if their plans are fixed like a timetable:
I start my new job on Monday.
What time do you finish work tomorrow?

Source: Essential Grammar in Use - Raymond Murphy - Cambridge