Let’s learn about it with a simple presentation
And now some exercises!
Exeercise 1 (about form)
Exercise 2 (only positive sentences!)
Exercise 3 (only questions)
Exercise 4 (only negative sentences)
FAST FINISHERS: http://www.englisch-hilfen.de/en/exercises_list/alle_grammar.htm (all exercises of Tense: present simple)