一、
一般现在时主要用于：
1 、表示经常性或习惯性动作。 e.g. It seldom snows here.
2 、表示现在的特征或状态。 e.g. He is always ready to help others.
3 、普遍真理。 e.g. Action speaks louder than words.
4 、剧情图片介绍，背景说明，动作解说。 e.g. (Tom enters the room and sits at the table)
Doctor ： What's your trouble,
young man?
Tom ： I've caught a cold, doctor.
5 、时间、条件、让步、方式状语从句表将要发生的动作时。
e.g. Tomorrow we shall go for an outing unless it rains.
与这种时态连用的时间状语常有： always, often, never, seldom, usually, once, a week, now 等。
二、
一般过去时主要用于：
1 、表示过去某个时间发生的动作或情况（包括习惯性的动作或状态）
e.g. When did you read the novel? She often came to help us in those days.
2 、谈到过去的情况时 e.g. I didn't know you were so busy.
3 、谈到已死人的情况时 e.g. Lei Feng was a great communist fighter.
与这个时态连用的时间状语常有：
yesterday, last night, the other day, two months ago, in 1985, then, just now, when, after,
as soon as 引导的时间状语从句，表示主句动作开始的时间。
三、
现在完成时主要用于：
1 、表示到现在为止这一时期中发生的动作或情况，即多次动作的总和。
e.g. We have learnt four English songs this month. How many times have you read the novel?
For many days we haven't seen each other.
2 、表示对现在有影响的某一已发生的动作。
e.g. The delegation has left 代表团已经走了（说明现在不在这里） Look, what you have done. 看你干的事。
与这一时态连用的时间状语有： already, yet, just, ever, never, by now, so far, recently, by the end of this month, since, for 短语，连词 since 引导的时间状语从句。
一般过去时与现在完成时的区别：
一般过去时：重在说明动作在过去发生时的具体情况（时间、地点、方式、对象、细节等）。
现在完成时：只提起已发生的动作（事实）及其影响，不说明动作发生时的具体情况。
cf. Have you had your lunch? What did you have for lunch?
I have ever been to the Great Wall, and I went there last summer with my father.
注：现在完成时表达的动作常具有反复性，故下面一句是错的：
Have you seen the six thirty's news program? 应改为： Did you see the six thirty's news program?
四、
现在完成进行时主要用于：表示过去开始的某一动作一直持续到现在，以至延伸到将来，它强调动作延续时间之长久。e.g. I've been writing an article. 我一直在写一篇文章。（还在写）
cf. I've written an article. 我写了一篇文章。（已写完）
It has been raining these days. 这些天一直在下雨。