1 英语中表达将来的时间有四种主要方式：be going to, will, 现在进行时，一般现在时。
2 Make a prediction. 若要预测将来， 可以使用 be going to 或者will, 此时两种词语的意思相同。
If Luis doesn't do something, the board is going to(will) ask him to step down.
3 will 在口语中与写作通常和代词一起使用。在日常口语也常和名词一起使用。
The company will probably do better next quarter.
If we don't work tonight, we won't have the report by morning.
4 Talking about definite plans. 谈论确定计划时，使用 be going to, be planning to 或现在进行时。不能使用will。
一般现在时也可以用来谈论将来的计划和安排，但是一般现在时只能使用一些特定的动词：arrive, leave, start, begin, end, finish, close, be.
Rupert is going to leave(is planning to leave, is leaving, leaves) tonight for France.
5 Expressing intention. 表达意向或者愿意做某事，使用will. 不能使用 be going to.
Can you meet me for 5 minutes today? Sure, I'll meet you around 4.
Don't worry about the report; I'll finish it tomorrow.
if you have a question, call customer service; they'll be able to help you.
6 Using present simple to express future time. 单词 when, as soon as, before, after, until 在一般现在时中通常放在主语和动词之前，用于表明某事将在未来发生。这些动词标志出将要发生的事情的次序：
首先Rupert到达，然后我们将开会。如果句子的某部分以 before, until 开始那么这部分通常出现在句尾。
① When(As soon as, After) Rupert arrives, we'll start the meeting.
② We'll start the meeting when(as soon as, after) Rupert arrives.
③ We can't begin the meeting before(until) Rupert arrives.