I searched over the net; only few irregular verbs exist: biti, htjeti, ići, moći, spati (spati is not so common, it's better spavati - to sleep).
Other verbs are regular even we don't have exact rules how to conjugate each one. For example (present):
trčATI (to run): trčIm, trčIš, trčI...
hodATI (to walk): hodAm, hodAš, hodA,...
pisATI (to write): pišEm, pišEš, pišE,...
And, yes, about irregular (present):
IĆI: idem, ideš, ide, idemo, idete, idu
MOĆI: mogu, možeš, može, možemo, možete, mogu
SPATI: spim, spiš, spi, spimo, spite, spiju