be going to / will
用于条件句时，be going to 表将来，will 表意愿
例句：
If you are going to make a journey, you'd better get ready for it as soon as possible.
Now if you will take off your clothes, we will fit the new clothes on you in front of the mirror.
一般现在时表将来
1)下列动词：come, go, arrive, leave, start, begin, return的一般现在时表将来。这主要用来表示在时间上已确定或安排好的事情。
The train leaves at six tomorrow morning.
When does the bus star? It stars in ten minutes.
2)倒装句，表示动作正在进行，如：
Here comes the bus. = The bus is coming.
There goes the bell. = The bell is ringing.
3)在时间或条件句中。
When Bill comes (不是will come), ask him to wait for me.
I'll write to you as soon as I arrive there.
4)在动词hope, take care that, make sure that等后。
I hope they have a nice time next week.
Make sure that the windows are closed before you leave the room.
