You have an instructor and a textbook, right?
You should have been taught that there are two major types of verbs (plus two main irregular verbs: kuru and suru). The two major types of verbs are sometimes called Type 1 and Type 2, but other terms may be used instead. The two types conjugate differently from each orher. Verbs ending in ru (hashiru, miru, kaeru, etc.) could be of either type, so for each of these ru verbs you must learn whether it is a Type 1 or Type 2 verb.
If you are not being taught in this way, it is probably inefficient. This is a standard way of teaching Japanese verbs.