There are approximately 180 irregular verbs. You don't need to learn all of them because some of these are very rare but many others are very useful and you do need to know them. What's the easiest way to learn them? Some people think you should learn a list 'by heart'. Others think you should not learn them at all – you will just gradually acquire them over time. One useful method is to note down new irregular verbs as you meet them. It is useful to write these verbs (or any vocabulary you want to learn) in sentences and learn those rather than the individual word. Which is easier to learn?