There are lots of tenses and lots of bits of tense related jargon to confuse both you and your student. But really, 90% of the time you’ll be using one of these five tenses – present simple, past simple, future, present continuous and present perfect. The first four are really pretty easy and sink in quickly. But present perfect will haunt most English students for years. It’s formed by using the verb have as an auxiliary with the present participle of the verb you are using.
There are two basic rules. Firstly, you use it when a situation started in the past and has recurred several times or is recurring in the present. “I have told you to open your book three times now!” Secondly, in situations where a single event in the past has an effect in the present. “I have read that book” implies that not only have you read it, but you remember what happens. It’s something you’ll come back to again and again and again. My tip is a simple one! Establish how you are going to teach this tense, what examples you want to use etc, and really, really, really focus on it till it’s drummed in good and proper! More so than any other bit of grammar.