Force yourself to write down what is of no interest, what is most obvious, most common, most colourless...antique shops, clothes, hi-fi, etc. Don't say, don't write 'etc'. Make an effort to exhaust the subject, even if that seems grotesque, or pointless, or stupid. You still haven't looked at anything, you've merely picked out what you've long ago picked out.
Don't you love it when people in school are like, “I'm a bad test taker”? You mean, you're stupid. Oh, you struggle with that part where we find out what you know? Oh. No, no, I can totally relate. See, because I'm a brilliant painter, minus my God-awful brushstrokes. Oh, how the masterpiece is crystal up here, but once paint hits canvas, I develop Parkinson's.