1. 时间标志词
一般现在时：often, usually, sometimes, always, every day,once/twice a week<br>
一般过去时：yesterday, just now, last week, three days ago,the day before yesterday , in 1990, in the past，often<br>
一般将来时：tomorrow, next week, this month, at once，the day after tomorrow, in an hour<br>
现在进行时：now, at present，look, listen，Ssh, be quiet, It's six o'clock.right now, at the moment<br>
过去进行时：at six yesterday morning, from 7 to 9 yesterday morning 、at this time yesterday, then<br>
现在完成时： already,yet, just, since,for,ever, never,before,by…, over...,in the past…,recently,these years,so far，up to now<br>
状语从句：if,as soon as, when,(主将从现)
2. 同句时态
and, but,when,while (从句的时态原则)
3. 上下文句意
找人系列
现在找人，某人正在做某事（am/is/are doing ）/某人已经去某地了(have gone to)
子主题
过去找人，某人当时正在做某事(was/were doing)
动词的发生前后比较（画时间轴）
