Years ago, I read that a great tip for compliments is to stick to stuff that people have chosen. So things like dyed hair, jackets with patches on, badges, band t-shirts, or indeed hair accessories.

It’s certainly possible to successfully compliment people on things they can’t change, like body features, but it takes more skill and can be risky if you don’t know the person. I spent a long while practicing giving compliments on the safer things that I mentioned, as a sort of ‘grinding social XP’ challenge, but I ended up really enjoying it