Teaching students to find the verb in their sentences is a really great way for them to see whether they have included ONE complete thought.
E.g. 'I went to the park it was fun' is a common type of mistake but it has 2 verbs- 'went' and 'was'. By identifying the verbs, they can see that they have two complete thoughts. They either need a full stop- 'I went to the park. It was fun.' or a conjunction- 'I went to the park AND it was fun.'