Once students are familiar with simple forms, it's a good idea to begin teaching continuous tenses. Start by teaching the present continuous and make sure that students understand the difference between stative and active verbs. Teaching the past continuous can be a little tricky so I prefer to introduce the idea of interrupted action early on. A fun way to do this is to use a flowery examples such as:
Jeremy was walking through the park. The birds were singing, the sun was shining and children were laughing and playing when he saw Anna. It was love at first sight.
This is silly example, but it helps students recognize the past continuous as a tense that paints a picture of what was going on when something important happened.