If a sentence has an auxiliary verb, the corresponding yes-or-no question uses the same auxiliary verb.

You are trying. → Are you trying?

We have ordered lunch. → Have we ordered lunch?

He can dance. → Can he dance?

We should call home. → Should we call home?

He was knocked down. → Was he knocked down?

If a sentence has no auxiliary verb, the yes-or-no question uses do (not be or any other auxiliary):

He tried. → He did try. → Did he try?

He usually comes on time. → He does usually come on time. → Does he usually come on time?

You need to know one more rule.

In sentences like He did try with an auxiliary verb followed by an ordinary verb, it is the auxiliary verb that inflects for tense and subject-verb agreement. So you say did try, not do tried or are tried. The other verb (try) is not inflected, except for the progressive, passive, and perfect.