We use the Present Perfect

in subordinate clauses of time introduced by the conjunctions when, before, after, as soon as, till and until where it is used to express a future action. It shows that the action of the subordinate clause will be accomplished before the action of the principal clause:

As soon as we have had some tea, Ann, we shall go to inspect your house. I'll take you back in my car but not till I' ve made you some coffee.

We use the Future Simple:

1 to express simple, factual predictions:

The newspaper says inflation will go up in the next few months.

2 to express a succession of actions in the future:

I' ll take a walk to the sea and on my way back I' ll buy you a newspaper.

3 a) to express hopes, fears, thoughts about the future, with verbs like think, hope, am sure, am afraid, believe, expect, etc:

I'm afraid I 'll get lost without a map.

Do you think the weather will change?

b) to denote actions whose realization is uncertain, doubtful, with adverbs perhaps, probably, of course and the like:

They' ll probably get a lot of satisfaction out of our quarrel.

Of course he will send you a letter in a few days.

4 to express a decision made at the moment of speaking:

O, wait a minute, I 'll come tomorrow instead of Friday.

We use the Future Continuous:

1 to express an action that will be taking place over a period of time in the future:

Don't come on Monday because I' ll be working all day.

This time next year, I' ll be taking my exams.

2 to speak about an action that will happen around or at a certain time:

He 'll be arriving at 7.

3 to be more polite and formal when asking questions about the future:

When will you be arriving?

4 to express an action which the speaker expects to take place
in the future in the natural course of events. The difference between the Present Continuous used to denote a future action and the Future Continuous becomes quite evident if we compare the following sentences:

We are meeting tomorrow (= we have arranged to meet tomorrow, we have fixed the date of our meeting).

We shall be meeting tomorrow (= not because of some arrangement but in the normal course of events; either because we work together, or because we attend classes together, or regularly play some game at the same place and at the same time, etc).