Past tense simple you mean, right? :) There are a lot of verbs who work "irregularly" but the main rules are these:
Šokti / šoka / šoko - to dance.
Aš šokau
Tu šokai
Jis/Ji šoko
Mes šokome
Jūs šokote
Jie/Jos šoko
Rašyti / Rašo / Rašė - to write.
aš rašiau mes rašėme
tu rašei jūs rašėte
ji rašė jie rašė
These are the two basic kinds of word endings for every verb in lithuanian in past. Some of them change the root, but basically end like this. Hope a native lithuanian can help you better than me, as i'm just learning too. Sėkmės, kaimyne! :)