1. 掌握主动关系用现在分词，被动关系用过去分词的基本原则。
① 分词做定语时，看分词同它所修饰的名词或代词的关系。分词所修饰的名词或代词同分词为主谓关系时，用现在分词；分词所修饰的名词或代词同分词为动宾关系时，用过去分词。
There are lots of good English language programs broadcast on TV or the radio in China.
过去分词短语broadcast on TV or the radio in China 作定语修饰programs, broadcast 同它所修饰的名词programs 具有动宾关系，即broadcast programs on TV or the radio…，因此必须用过去分词。
Two days later I received a letter offering me the job.
现在分词短语offering me the job是名词letter的定语，offering同它所修饰的名词letter具有逻辑上的主谓关系，如果将现在分词短语转换成定语从句，这种“主谓关系”则更为明确：Two days later I received a letter which offered me the job。
② 分词做宾语补足语时，看分词同宾语的关系。主谓关系用现在分词；动宾关系用过去分词。
You often see musicians performing in the streets.
宾语musicians和宾语补足语performing 具有逻辑上的主谓关系，musicians发出perform 的动作，宾语补足语必须用现在分词。
Although we may not realize it, when we talk with others we make ourselves understood not just by words.
作宾语补足语的过去分词understood同宾语ourselves 为动宾关系，即understand ourselves，此处的意思是“使我们自己被别人所理解”。
③ 分词作状语时，分词的逻辑主语同句子的主语一致。据此，辨别现在分词和过去分词的区别要看分词同句子主语的逻辑关系，主谓关系用现在分词；动宾关系用过去分词。
In Arab countries, you eat using the fingers of your right hand; the left hand is not used at all.
现在分词短语 using the fingers of your right hand 作方式状语修饰谓语动词eat。之所以用现在分词，是因为using 同句子的主语you 有逻辑上的主谓关系。换言之，句子的主语 you既发出谓语动作eat，又发出非谓语动词using 所表示的动作。
Dr. Watson and I will spend the night locked in your room.
过去分词短语locked in your room充当spend the night的方式状语。lock 同句子的主语Dr. Watson and I的逻辑关系为动宾关系——“lock Dr. Watson and I in your room”。
分词作状语时同句子主语之间的逻辑关系较难理解，再看以下例句，注意分词短语同句子主语之间的逻辑关系。
The poor of the cities and the peasants in the country, having lived such a hard life for so long, took up their guns and knives and began to kill the rich nobles.
Considering that Charles would be sentenced to death, he went to a chemist’s shop and bought some special medicine.
Given advice by the famous detective, the young lady was no longer afraid.
The lady returned home, followed by Mr. Holmes and Dr. Watson.
2. 分词作表语时，区别现在分词和过去分词的两种方法。
① 分词作表语时，现在分词表示主语的特征；过去分词表示主语所处的状态。
The temperature is –15°C. It is freezing outside.
现在分词freezing作表语，表示主语“天气”的特征。
Children are afraid of the stone figures in the temple which look so frightening.
which代表先行词the stone figures 的含义，在定语从句中作主语。frightening是系动词look的表语，表示主语the stone figures的形象特征。
One quarter of the shores of the Mediterranean are polluted.
过去分词polluted作表语，表示地中海沿岸的四分之一受污染的状况。
② surprise, excite, interest, frighten, worry, please, 等动词具有共同的特点，他们的意思都是“使……（人）…怎么样”。
这类动词充当表语时区别现在分词或过去分词的方法比较简单：如果主语是表示“人”的词语，表语用过去分词；主语是表示“事”或“物”的词语，表语用现在分词。
We were getting very worried.
“The lion! It must be the lion from the zoo!” Mrs. Cousins was frightened.
以上两句的主语分别是 “we”和 “Mrs. Cousins”，表语用过去分词worried 和frightened。
The news that the Chinese team won the gold medal was very encouraging.
主语是表示“事物”的词语the news，表语用现在分词encouraging。