Since I don’t have a normal badge, does this mean I’m allowed to correct everyone or no one. 
Back on topic. I first heard the “rule” about no kana between the kanji and る meaning it’s godan even if it rhymes with いる・える several months ago, and anecdotally I’ve found it to be true often enough that it’s worth using as a default for words you don’t know. Someone could always go through all verbs in this form and get some actual statistics on it, but that sounds like a lot of work…
What about せかるる? It has two るs in a row and that scares me.
Dunno how much of a tip this is since, frankly, I didn’t follow it all the time, but in Japanese class we memorized verbs in their dictionary form and masu-form. Apparently this was so we could more easily remember if a verb was a godan or ichidan verb, but I’m not sure how feasible that is long term. Probably works for some people out there tho
After more experience it’s less about memorization and more about feel. Let’s say I was trying to remember if 入る (はいる) was ichidan or godan. I would try saying 入ります and 入ます. I’d also try saying 入った and 入た. In this case, I immediately recognize that 入ります and 入った sound right, meaning it’s godan. Of course, this doesn’t help as much with words you’ve never seen before or see rarely, but even then it might help a bit as you get more and more used to the sound of the language.
I was doing the same thing 
Although I found it not accurate enough some times since there are a couple of exceptions which make this practice misleading, like e.g. conjugating 帰る to 帰ります feels right and 換える to 換えります also feels… somehow right 
Or maybe I was just too lazy to properly memorize such “exceptions”.
But it definitely makes you used to the sound of the language, thats for sure
Thanks for mentioning that, I am also doing it. It’s a huge help when I try to conjugate such word later since they more easly pops out into my mind. Without that I need to spend considerable amount of time thinking if how to conjugate such verb and then just double check if it’s not gibberish
Great content, it’s been stuck on my ‘to watch’ for way tooo long. And now I watched it. Thanks for the push Leebo 
I know I’m a bit late with this but it might help someone. This Tofugu article really helped me get a handle on verb conjugation groups, hopefully it can do the same for others as well.