http status codes for api error handling. best practices, dont you think?

hey folks, i'm trying to nail down our API's error handling and wanted to chat about the best way to use http status codes. we've got a jumble of 400s, 404s, 500s, and some of our own codes too. what do you usually do? any codes you avoid or always reach for? how do you deal with it when a request is technically a 400 bad request, but it's also about a specific thing that's not there, like a 404