designing for idempotency in APIs, best practices?

so, i've been thinking a lot about api design lately, especially about idempotency. it's super important that sending the same request again doesn't mess things up, right, particularly when the internet's a bit shaky. what are your go-to ways or patterns for making your apis idempotent? do you use certain headers, how you structure requests, or specific database tricks? really curious to hear how you all do it.