正在进行时态的标志词主要包括以下几类：
一、基本标志词
时间副词 now
（最常用）：如：
> I am reading a book now.
at the moment：如：
> The meeting is starting at the moment.
currently：如：
> The project is currently on schedule.
right now：如：
> The phone is ringing right now.
this day/week/month：如：
> We are organizing the event this week.
动词ing形式 通过be动词（am/is/are）+动词ing构成，例如：
> She is singing beautifully.
> They are playing football in the park.
二、其他辅助标志
时间状语
right now（强调此刻）：
> The weather is terrible right now.
this afternoon/night： 如： > We'll meet this afternoon. soon
> The meeting will start soon.
上下文提示
动词本身具有进行时含义（如：
> The company is expanding. [grow]
> The river is flowing. [flow]）
三、使用注意事项
与现在完成时区分
现在进行时强调动作的进行状态，而现在完成时强调过去动作对现在的影响（如：
> I have finished my homework. [强调结果]
> I was reading when the phone rang. [强调过程]）
与一般过去时区分：
现在进行时用于描述当前动作，一般过去时用于描述过去已完成的动作（如：
> The movie started 2 hours ago. [过去时]
> The movie is exciting! [现在时]）
通过以上标志词的灵活运用，可以准确表达动作的时态特征。