1 - Present simple as a future:

- timetables, starting times of meetings...
- Conditional (1st type): IF Present simple + Will (we refer to the future)
- we use the present simple after adverbial sentences (when, while, before, as soon as, until, after, if...).

..El present simple (con sentido de futuro) se utiliza para hablar de programas, horarios, agendas, etc. oficiales y, por lo general, se utiliza con sujetos inanimados (aviones, trenes, instituciones, etc.).

1-
. The train leaves at 3 o'clock.
. The school meeting starts at 4 o’clock.

. If you give me your address, I will send you a letter.

. The bus arrives at 8 o’clock tomorrow

2 - WILL:
- to make predictions based on what we think or imagine will happen in the future
- to make quick decisions: the action is decided at the moment of speaking

- Verbs: think, believe, hope, expect... be sure, be afraid...
- Time expressions: probably, certainly, perharps... (the adverbs definitely and probably come before won't, but after will).
- simple facts we can't change (weather...)
- When (= what time) + will

- a fact or truth (I will be thirteen on June the 1st)

..Usamos Will + infinitive para expresar decisiones espontáneas o reacciones rápidas tomadas justo en el momento. También para hacer predicciones basadas en los que pensamos e imaginamos (con verbos como: think, hope, expect, believe, promise...; expresiones: be sure, be afraid...; y con adverbios como probably, perhaps, certainly...) y para promesas, peticiones...

2-
. I think I will go to your birthday party
. My sisters probably won't be there.
. I will open the window.
. Will you help me do my homework?
. I will probably be there.
. When will I see you?
. I don't know when he will be back.

3 - BE GOING TO + infinitive:
- premeditated intentions and plans in the future (an action you decided to do)
- to make predictions based on what you can see now (real or present evidence)

..Usamos BE going to + infinitive para intenciones y planes o ambiciones futuros, para predicciones basadas en lo que vemos o sabemos, tenemos evidencia en el presente.

3- I am going to work in the UK for two months.
. I am going to buy a new computer

. Look! Be carefull! You're going to drop your books

. It's very cloudy. It's going to rain this afternoon

4 - Present continuous: (future meaning)

- a fixed future personal plan, date or arrangement in the near future
- actions happening now (right now, at the moment)
- Time expressions: tonight, next month (year, week), tomorrow, this weekend, etc.

..El present continuous se utiliza para hablar de planes o citas concertadas que tenemos a nivel individual; son bastante seguros que se realicen, y llevan una expresión temporal o complemento circunstancial de tiempo.

4-
. She is coming home tonight
. I'm meeting him at 10:00

. We are meeting some friends tonight

. I am visiting my friends next weekend.

- future arrangements and plans.

- offer to do something, a voluntary action

- unplanned, spontaneous or quick decisions...