"Who? - He!"
Translation:Wer? - Er!
This exercise opened my eyes; Before I would see 'Wer' and think of 'where'. I found it hard to remember that it was refering to 'who'. Now when I see 'wer' or one of its variants I think of the 'w' sound being attached to 'er' he. Making it a 'what question' in my consciousness. This allows me to quickly see 'wer' and associate it with 'was ist er' or in the gramatically correct variant 'wer ist er?'.
https://www.grammarly.com/blog/who-vs-whom-its-not-as-complicated-as-you-might-think/ I used this for Who and Whom