Hmm, I hope my reply wasn't too late. If so, maybe you can use this post for future reference?
Irregular verbs in the Preterite are pretty common. The most used would be "Ir, Ser, Ver and Dar", although the first 2 are essentially the same - fui, fuiste, fue, fuismos, fuisteis, fueron
Other verbs are grouped according to changes:
Car, Gar, Zar : verbs in this group change in the 'yo' form
example: jugar -> jugue
J Group : verbs in this group change to a j sound
example: trajer -> traje
V Group : verbs in this group change to a v spelling
example: estar -> estuve
P Group : verbs in this group change to a p spelling
example: saber -> supe*
*I can't recall now if there are more like this, but saber is a verb you'll be using a lot. Remember, in the preterite, it means "to have found out"
Apologies for not beign able to add accent marks. Try these site:
http://www.drlemon.net/grammar/irreg-pret.html
http://www.rocketspanish.com/spanish_preterite_irregular.php
And here are three to help you out:
Yo fui ala escuela porque yo olvide mi libro
?Tuviste una lapiz que yo puedo usar?
Mi madre me dijo, limpia tu cuarto!