Allow me to introduce to you, what I like to call, the three silent “Superstars” of the English Grammar: the verbs “Be”,Do” and “Have”!
Of course you’ll often see them holding the main role in a sentence, like in the following:
      1. I am a student.
      2. I have a sister.
      3. I do my homework. 
That’s not all they can do for us though.
More often than not, they help us “build” most of the English Tenses and are thus very very important – even when they take on the role of an “auxiliary”.
Like the auxiliary police in your local city or town, they’re not the main crime fighting force, but they can make all the difference in putting things in order -or cell for that matter 😀 – helping, assisting, supporting the community.
In the exact same way, Be, Do and Have often carry no meaning while supporting the main verb in a sentence, BUT they help us communicate a lot about the time, the conditions, the frequency and all sorts of other information related to the action being described.
So, you might think, I know I need them, but I never know which one to use and when! What do you say we put them all in cells too and see if that helps clear things up a bit? 
Have a look at the following chart:
So then we have:
  • DO for Present and Past Simple
  • BE for all Continuous Tenses – [Think Verb-ing, ongoing actions]
  • HAVE for all Perfect Tenses [Think past participle, verb-ed – completed actions]
How about an example?
Of course there’s always more to a story than a couple of charts and noodles! 😀
But hopefully, this can help serve as a general guideline for all your.. active (voice) language wear 😉
Print it, pin it and most of all, use it!
Till the next time!