I had an aftershow pass when Lemmy put me on the guestlist but because of the retarded staff at the venue I didn't get to see him (or even thank him). There was someone without a pass that was telling me and the staff that he loved the band and wanted to meet Lemmy - he didn't get to see him either.
If you have an aftershow pass you would probably not have trouble meeting him. Without a pass you would have to catch him going to the venue or leaving. I'm not sure if he would pose for a picture if you caught him as he was entering the venue. If you were a pretty girl or if you had a pretty girl with you, you would have more luck.