There are twelve tenses of the English language; some of them are very similar, some are very unique, some have concepts behind them which are easy to grasp, and others are more elusive. The key to teaching the tenses or any grammatical concept is the same: never start the class with the grammatical form and rules. Instead you want to use an interesting idea, question or anecdote that happens to employ the designated tense that you'll be teaching that day, but that secures your students' interest.
Give interesting examples. Don't start class with the grammatical form of a given tense written on the board, start with a story, picture, skit, movie clip, that showcases that grammatical concept. For example, if you're teaching the present simple tense to talk about habits, show your class your coffee cup and tell them: \"I always drink coffee in the morning.\" Show them your car keys and say \"I usually drive to work.\"
Get your students to mirror your example and the language that you use. Ask your students what they always do every morning. Ask them what they usually do. At this stage, if a student makes a mistake, just correct them gently by repeating what they were trying to say in the correct form.
Put the basic form of the present simple (or whatever tense you're teaching) on the board with a variety of regular verbs. Show your students how the verb changes in negation and question form. Answer any questions.
Give each student a controlled practice exercise that tests their understanding of the present simple. This exercise can be a gap-fill, or ask them to find the errors or something equivalent. Check answers as a class.
Put your students into pairs for a freer practice exercise. Ask them to interview each other about facts regarding their lives and habits. Make it clear that each question and answer must be given in the designated tense you taught that day.