tl;dw of that Cure Dolly video (copy/pasted from a post I made earlier):
Verbs that end with ～ある sounds are almost always intransitive, just like ある is intransitive.
Examples:
- 上がる
- 下がる
- 分かる
- 代わる
- 止まる
- 当たる
- 回る
- 決まる
- 助かる
- 終わる
- 転がる
Verbs that end with ～す (or ～せる) are almost always transitive, just like する is transitive.
Examples:
- 出す
- 正す
- 写す
- 申す
- 足す
- 直す
- 回す
- 思い出す
- 見直す
- 話す
- 欠かす
- 表す
- 返す
- 通す
These are all vocabulary words from the first 10 levels in WK. In those 10 levels, the only exceptions to these trends that I see are (coincidentally both in Level 10):
- 語る (transitive)
- 配る (transitive)
Most verb pairs include a word with an ～える sound, like 止める, 当てる, 終える, or 出る for example. These verbs just flip the transitivity of their partner verb.
EDIT:
Simply speaking, the difference between transitive and intransitive verbs in Japanese is whether or not the verb takes a “direct object” marked by を.
The two exceptions in the first 10 levels of WK shouldn’t be hard to remember, because without a direct object, those words would simply say, “I/he/she recited,” or “I/he/she distributed.”
Recited what? Distributed what? Those “what’s” take を, which is what designates 語る・配る as transitive:
[なにかを] 語った・[なにかを] 配った → “(I) recited [something]” “(I) distributed [something]”