What is the best way to make a content negotiation request for any DOI?

Content negotiation is possible for all DOI Registration Agencies (e.g. DataCite and Crossref) via doi.org. Following the guidance outlined in the documentation, you can make a content negotiated request like this:

$ curl -LH "Accept: application/vnd.citationstyles.csl+json;q=1.0" https://doi.org/10.1021/acs.joc.0c00770

DataCite's content negotiation service is available at https://data.datacite.org and only supports DataCite DOIs.