1.是否定句之后通常用 or代替 and.如：
He spoke loudly and clearly.他说话声间宏这且清晰.
He didn’t speak loudly or clearly.他说话声音不大且不清晰.
2.祈使句＋and =if,而祈使句＋or = unless.如：
Work hard,and you will succeed.(=If you work hard,you’ll succeed.) 努力工作,你就会成功.
Work hard,or you won’t succeed.(＝Unless you work hard,you won’t succeed.) 努力工作,否则你就不会成功(from www.***.com).
3.有时 and与 or可换,如：life and (或or) death (在死)；有时and no与or互换.如：
He has no brothers and no sisters = He has no brothers or sisters.他没有兄弟姐妹.
4.在选择疑问句中,用or 不用and.如：
Is it a pen or a pencil?那是钢笑还是铅笔?
Which is bigger,the sun or the earth?太阳和地球哪个大?
5.在both 之后用and,在either之后用or.如：
Both you and he are right.你和他都是对的.
Either you or he is right.不是你对就是他对.