Practise the past simple of the verb to be:
http://www.better-english.com/grammar/was2.htm
http://esl.about.com/library/beginner/blwas.htm
http://www.ego4u.com/en/cram-up/grammar/simple-past/exercises?03
Do the Level 2 game: http://www.funbrain.com/verb/index.html