有冇人可以救下我D Tenses!!

Actually you often have to understand the whole paragraph or at least what is going on so you can judge what tense should be used. By simply looking at one particular sentence you have a good chance to get it wrong or getting confused in the process.

Basically personally I think of the timeline of English as a horizontal line, you will often need to know where is NOW on the line and mark it with your head, then read the sentence or paragraph, what are the times at which those events happen compared to NOW, also what do the sentences really meant to say?

1. Simple Present (always, every, never..)
- I swim every Saturday. (routine)
- The sun rises once a day.
(widely considered as truth, something assumed to always happen)
- "I see nobody but I can hear someone sneaking nearby !", Chavez whispered.

2. Present Continuous (at the moment, now..)
他即使之前已被叫停卻還是在不停的寫
- He is still writing even he has been told to stop. (his action is still in process NOW)
她這星期天將會去探望她的母親
- She is going to visit her mother this Sunday.
(the action is planned and believed to be carried out as planned)

3. Present Perfect (already, since..)
- I have finished my homework already.
(the action/task/event is completed/happened at some unspecified time before NOW)

4. Present Perfect Continuous (since.. often lacking words as hints, have to understand what the sentence/paragraph meant to say, can apply with or without indicating a specific time)
我們相信這逃犯於上年越獄之後一直還在匿藏
- We believe this fugitive has been hiding since his escape from prison last year.
(an action is carried out since last year and still in progress even NOW)
有謠言宣稱政府一直在進行非法武器研究
- There are rumours that the government has been conducting illegal weapon research.
we do not know when it was started in the past, but we think it is still in progress NOW

5. Past Simple (ago, 1987, last year..)
- He was a Champion 10 years ago. 他十年前是一名冠軍
- He answered the phone, "What do you want?"
(here time is not specified, but we usually know it from somewhere else that it happened in the past for example in novels we know the background of the story. Besides, the author cannot tell his story without the story already happened unless he used an unusual writing technique)

6. Past Continuous
我不是你要抓的小偷, 案發時我還在和經理吃晚飯呢
- I am not the thief you are looking for. I was having dinner with the manager when it happened.
(the time when the theft happened is treated as NOW)

7. Past Perfect
我在加入(joined)本公司之前曾受過一些有關培訓
- I had had some related training before I joined this company.
(the time when I joined the company is treated as NOW, something happened sometime before I did something)

8. Past Perfect Continuous
- I had been eating all day long before the buffet even began.
那自助餐還沒開始(began)我便經已整天沒停的在吃
(similar to present perfect continuous but treat NOW as the moment when the buffet began, since some unknown time before the buffet began, which is in the past, that action has been going on)

9. Future simple
- I will catch you someday. 總有一天我會抓到你的
- She will go to visit her mother this Sunday.
她這星期天會去探望她的母親

10. Future Continuous
- When his wife arrives the airport tonight, he will be having dinner with his mistress.
他老婆今晚到達機場的時候, 他會正在與其情婦共晉晚餐呢

11. Future Perfect
- He will have finished his assignment by the time he come back to Hong Kong next week.
他下星期天回港時他會經已完成他的工作了

12. Future Perfect Continuous
- I will have been waiting for ages when she finally turn up.
當她終於出現的時候我便經已等候了世紀般久了

They are basically all quite similar to each other, mostly just the place of NOW on the timeline is different.

The simple present tense is used to
1. express a gact that is always true 當一Ｄ野係事實
The earth goes round the sun. 地球繞地球轉. [呢個係不變的事實]
2. to express a hotbit
i do not eat anything before i go to school every day.
3. to express an action which is done everyday
she goes to school by bus everyday.[如果個He She It 現在式後面個verb加s or es]

present continuous tense is used
1. to express what is actually happening at the present moment of speaking.[發生緊ge]
i am doing my homework now.
2.to express what will happen in the future[將來會發生]
i am going to see Mary tomorrow.

the present perfect tense
is used to wxpress an action that began in the past and has been finished at the time of speaking or is still continuing.
[表示以前發生的事情，繼續發生到說話的時間]
I have just opened the window.

the simple past tense
is used to express an action done in the past.
i went to USA last month.

the past continuous tense
is used to show an action that was going on at a certain time in the past, mostly it is used when two things happened at the same time.[以表示過去發生的事情，係表示兩種事情係差唔多時間發生]
when he came in i was doning my homework.

the past perfect tense
is used to express an action that happeded before another action at certain time in the past, therefore it cannot be used alone in a simple sentence. it is used with the simple past tense.
eg. i had wtitten a letter before i went to bed.

future continuos[將會發生ge]
is used to ecpress an action which i s going to happen.
he will go to Japan next week.

幫你搵了條link，睇下幫唔幫到你？

http://www.npc.edu.hk/staff/~ngtungying/english_grammar/lessons/lesson32.htm