How old are your students?
I use these worksheets on tenses:
tenses worksheeets with affirmative, negative and questions formation
(the tense worksheets are about half-way down the page.)
But I actually teach them present continuous first, past second, future third and then present.
Anyway, the main concept for the present tense is that it is independent of time. That is to say, if we have a time line of events, the present tense would never fall on it. So, once my students have a good idea of the concept of time and events on the time line, I can explain that we have things that are independent of time and that is the 'no-time' tense.
So, things that are true now and independent of the time line are expressed in the present tense.
"My name is Mark."
"I like sports."
"I have 2 sisters."
"I don't kink mushrroms."
"I want a new car."
*Language isn't a rule system and so that doesn't work for all verbs. Some of the state verbs that don't use the present continuous can cause confusion. So initially you might want to avoid using 'have' - holding, 'live', 'love', etc.
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