[1] Susan Benesch of the Dangerous Speech Project has articulated a taxonomy of counterspeech which includes eight specific strategies.
They include the 1) presentation of facts to correct misstatements or misperceptions; 2) pointing out hypocrisy or contradictions; 3) warning of possible offline and online consequences of speech; 4) identification with original speaker or target group; 5) denouncing speech as hateful or dangerous; 6) use of visual media; 7) use of humor; and 8) use of a particular tone, e.g. an empathetic one.
Two of the most prominent of these are I Am Here International and the Online Civil Courage Initiative (OCCI), a partnership between the Institute for Strategic Dialogue and Facebook.
[4] A Swiss study reported in December 2021 on a field experiment using three different strategies of counterspeech, using single responses to xenophobic posts on Twitter: humour, warning of consequences, and empathy.
It found that only empathy had a small but measurable effect on the hate speech, with the authors suggesting that future research should focus on repeated interventions.