Intermediate II. Past Tenses

As they say "practice makes perfect", quite a convenient saying in this case. Practise past tenses through the following online exercises:

Simple past or present perfect?

http://www.englisch-hilfen.de/en/exercises/tenses/check.php

http://web2.uvcs.uvic.ca/elc/StudyZone/410/grammar/ppvpast1.htm

Past perfect contrasted with other past tenses.

http://www.englishpage.com/verbpage/pastperfect.html

Irregular verbs:

http://www.englisch-hilfen.de/en/exercises_list/verbs.htm
http://www.englisch-hilfen.de/en/exercises/verbs4/index.php
http://www.englishpage.com/irregularverbs/interactiveirregularverbs1.htm