Pretending to be interested in, or experts at, things they've heard you say you like. Then it turns out they know nothing about it whatsoever.

I went on a date once with a man who had claimed to be a professional singer and guitarist in a local band. He had read in my singles ad that I enjoyed music. I come from a family of musicians, and had also been married to one.

Sidebar lesson: Probably not a good idea to go to a guy's apartment on the first date. 1.) When I got there, he claimed that the reason he had no guitar was because it was in the repair shop being restrung. Any professional would own more than one instrument, for just such a reason. Something happens to the one they normally play, they've got a backup at the ready. 2.) Any guitarist worth HALF a darn can restring his own instrument in a few minutes. It's less complicated than putting new laces in your shoes. You wouldn't need a shoe repair shop to do that, would you? 3.) When he sang along with the radio, he was absolutely tone deaf. 4.) At one point, he insisted that no, it is impossible, it is never done, you *cannot* change the key in the middle of a song. It's called "modulation," and it happens all the time. Anybody who makes a living playing music would know that.

That's not even all that was wrong. Obviously this guy was no musician, and no, his intentions were not innocent. I never saw him again.

So to recap, watch if they're blatantly wrong about something they claim expertise in.