建议不要细抠所谓的规则,否则容易机械化!英语也是语言,宜活学活用,积累重要语言点（一些实实在在的例句,而不是所谓的“规则”）,培养语感.
以下供参考!
从结构上说,英语连接词分两大类：并列连词（coordinating conjunctions）和从属连词（subordinating conjunctions）.并列连词连接两个或两个以上地位平等的字、词组或分句.例如：(1) Air and water are indispensable to me.(2) She likes going out with friends or playing outdoor games.(3) Most workers have a good income,so they look very happy.从属连词连接两个或两个以上的分句,形成复杂句中的从属分句.例如：(4) He said that he did not want to go .(5) Many things have happened since I last saw him.(6) You may come if you want to.从属连词用来连接各种从句.until(till)直到,在用until表达时间状语的句子中,主句中的动词是要十分小心去选择的.如动词是持续行动词,它要用肯定句,如：I studied hard until 12 o'clock last night.如果动词是瞬间截止性动词,则要用否定句,如:He didn't go to bed until his mother came back.由since,for,by,before,来引导的时间状语从句.since 引导的时间状语是动作的开始时间,如:I have studied English since 1990.而by引导的时间状语通常是动作的结束时间,如：I had learned 25 English songs by the end of last term.