Find the forms of the irregular forms and learn them: To buy, to choose, to pay, to do, to hear, to know, to misunderstand, to spend, to tell, to see, to rise, to mean, to shake, to send, to become, to fell.
To buy- bought -bought
to choose-chose -chosen
to pay-paid-paid
to do-did- done
to hear- heard- heard
to know- knew- known
to misunderstand- misunderstood - misunderstood
to spend- spent- spent
to tell- told-told
to see-saw-seen
to rise- rose- risen
to mean-meant-meant
to shake-shook-shaken
to send-sent-sent
to become- became-become
to fell-fall- fallen