Does anyone do this - how do you approach people and what are the best effects?

I don't do it, but if I were to do it I would try Tony Griffith's Pseudo Psychometry. Great audience participation, funny, enough going on to keep and draw an crowd, and a pay off ending. I would change the props and maybe use Fogel's(?) bags instead of envelopes.

Technically it is not metalism, but mental magic.

There was pretty active discussion on this topic here this a short time ago. Try using the search facility and see what you can come up with.

BroDavid