As I understand it, if a verb is a weak verb, I can extrapolate every form of that verb using basic grammar rules. All I need to know is the verb's infinitive form.
But for non-weak verbs, I need to know if the stem changes, how it changes, and in what situations.
Right now, I am looking at a book of verbs which has a huge list of conjugations, but most of them can be reliably deduced, right? So what is the least amount of information one needs to be able to deduce everything about a verb?
It looks to me like you need to know: the infinitive form, every form the verb takes in the present tense (for verbs like sein), the past participle, the imperfect stem, and whether the perfect is formed with sein or haben (in addition to the meaning of the verb, of course).
But I am sure I am missing something!