Postby a_cubed » October 1st, 2010 1:12 pm
Verbs ending in aru, uru and oru are all class 1: ~arimasu; ~urimasu; ~orimasu. With iru and eru verbs you just have to learn. One thing I've noted is that for many (though not all) verbs with transitive and intranstive variants, one is often class one and the other class two, so that can help. E.g. tomaru/tomeru. tomaru conjugates to tomarimasu and tomeru conjugates to tomemasu. I have come across at least one verb which doesn't follow this (can't remember which it was offhand) but it can be a useful helper. When I'm memorising verbs, I always try to remember the masu-form and the dictionary form, which provides all the needed information.