New answers tagged particle-で
忘れないで here is the casual form of 忘れないでください, which means "don't forget". In general, when it's not the last word in the sentence it means "without forgetting". As you guessed, it's basically one of two て forms for negative verbs. The other is 忘れなくて, but it's used in different contexts like 忘れなくてもいいです, "it's alright if you forget".
As for 待つ, it's always used with で. I don't know when to use に. As for 寄る, に is used in the same way as ～に行く ("go to ～"), ～に来る ("come to ～"), ～に向かう ("head to ～"), ～に送る ("send (something) to ～"), etc. It's the primary particle that marks a destination. That said, you cannot always expect a logical answer for this kind of question. You may find this ...
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