I like to say that the aspect is what exactly is more important for the speaker: the result (perfective) versus the very fact of being in process of activity (imperfective) keeping in mind that starting or completing the activity viewed as the result.

Remember about aspects of the verbs of motion (uni(multi)directional) if you want to describe all.
Usually I say that multidirectional verbs describe a kind of long process consisting of several tasks (dividable) while unidirectional verbs are atomic or instant. They describe an instant state of art (imperfective) or an instant event (perfective).