Verbix, uma ferramenta online útil:

Verbix — study and learn the verb grammar, conjugation and inflection of: Afrikaans, Asturian, Batticaloan Portuguese, Cape Verdian, Catalan, Danish, Dutch, English, Esperanto, Etruscan, Faroese, Finnish, French, Galician, German, Gothic, Hausa, Hindi, Icelandic, Ido, Interlingua, Irish, Italian, Jamaican, Jiwarli, Kreyol, Kreyol Louisienne, Latin, Latino sine flexione, Martiniquais, Master Language, Middle High-German, Norn, Norwegian (bokmål), Novial, Occitan, Old English, Old Norse, Old Occitan, Old Scandinavian, Old Swedish, Papiá Cristang, Papiamento, Português de Corlai, Portuguese, Proto-Indo-European, Rhaeto-Romanic, Romanian, Runic Swedish, Sardinian (Logudorese), Setu, Shona, Spanish, Sranantongo, St.Lucien, Swahili, Swedish, Tamil, Turkish, Urdu, Welsh, Volapük, Wolof.

Ou seja: se você não sabe como conjugar aquele verbo maluco no pretérito mais que perfeito não há mais problema.