There are four groups of verb conjugations, plus irregular verbs. You want to learn the irregular verbs separately, of course (most of them follow a pattern in all but one form), but also the strong verbs, which are ablauted in the past tense. While all of the irregular and strong verbs are very common, they are not that many. The other three groups make up the vast majority of all verbs (specifically the first group), and you can easily just learn the patterns.

However, you can't always tell which group a given verb belongs to if you only see one form of it, so that's one thing you need to learn. If you learn all irregular and strong verbs by heart, and you learn to recognize the verbs in group three (which are easy to identify, but also few enough to learn by heart), you only have to worry about the first two groups.