Subject Questions

Subject questions have no subject in the question. Any present / past simple verbs should go in the past / present simple tense, not the infinitive form.
  
   Only What and Who can be used in this kind of question.

Question word	verb	object
Who	likes / needs / wants is following / calling saw / called	me / you / him / her / us / them? the film?
What	happened (to is happening (to	me / you / him / her / us / them?)

     Who likes me? What happened to you?

     In the present tense, always use the third person singular form of the verb.
     What happens next?           NOT            What happen next?

Common mistakes:
1)            Some students use an auxiliary verb in an subject question.
     What did happen?         =>     What happened?
     Who did meet you at the station?=>     Who met you at the station?