Ichidan verbs end in "ru", but many verbs that end in "ru" are godan. Once and for all, I just have to remember that ichidan end in "ru" and drop the entire "ru" and replace it with the conjugative suffix; and so the previous kana stays the same (one column). The godan ones fracture the last kana, changing it into the four siblings in the same row (or else replace it with って or った). If we have a -ru verb and the -ru goes to -ri to make the stem, that indicates godan (帰る→帰り→帰ります); if it just drops to make the stem, godan (見る→見→見ます）. I have no need to tell which is which, other than discussing grammar with other gaijin. I would never remember that a verb is supposed to be godan, in order to then know how conjugate it; I already know how to conjugate it and so just for academics, I have to remember which pattern is classified as which conjugation.

An important aspect of vocabulary that informs you about verbs is knowing the nominal: the noun-like stem. Like when you consider 帰る, you know from your vocabulary that there is no noun-like word "kae" that is just written 帰. You know that "homecoming" is not "kae" but "kaeri", 帰り.

So from that alone you know instinctively which way it conjugates: らない、れない、りたい、った、って、ろう、。。。

And a big source of learning the stem is ... japanese polite speech with -masu.

This is how children absorb what the stems are: hearing all the verbs in -masu form.

For instance, I think that every single verb that ends in "-rimasu" in the polite form (other than just arimasu?) is a godan -ru word. Drop the masu and you have a -ri stem, which implies the word is -ru, and conjugates godan: -ranai, -renai, -ritai, -rō, -tta, -tte, ...