Some rules in Toefl Grammar :
1. Passive voice : be + v3
Present : am/is/are + v3
Past : was/were + v3
Present perfect :have/has/been + v3
Future and modal : will/must/can + be + V3
2. Correct sentence : S + V
eg : Johny watching tv coming here
This is a wrong sentence because that sentence only has a subject.