英语怎样才能分辨出一般过去时等等之类的?

需要观察句子里面的动词时态,就是主语后面的那个动词的时态.
is am are 是be动词 现在时态／ was were 一般过去式／ have been,have done 现在完成式／ had been,had done 是过去完成式
go,watch,do.实意动词的 现在时态／ went watched did 一般过去式／ have gone have watched have done 现在完成式／ had gone had watched had done 过去完成式
can may 情态动词 现在式／ could might 过去式
或者是通过具体的时间状语来判断,例如,yeaturday,last year,1950,