Through out the year I will get asked a million time about leave-behinds and other assorted promotional items. I just received the question again, and this time I'm just wrapping up the con season and have a nice fresh perspective on the issue. Let me start out with the most important point about self promotion. Have a leave behind. I was floored that on numerous occasions this year when I asked for a business card or some other self-promo piece so that I could remember an artist and share their work with the other AD's back at the office I was told that the artist didn't have anything to share. Seriously? If you want to be forgotten or passed over follow this example if you want a shot at getting some work.
There, that's the easy part. After that bit of advice it gets a lot more complicated. This year I saw everything from standard business cards, custom business cards, post cards, mini portfolios packs, self published comics, self published books, and in one case a custom sketch with contact info ('cause they ran out of cards). Which one worked best? Which form of leave-behind got more notice? Tough to say... Let me tell you how I use leave-behinds. I look at hundreds of portfolios during a typical convention weekend. I use leave-behinds to kick start my brain about who and what I saw during the day/weekend/week.
I also take the pieces back to the office (if I can fit them into my luggage... consider that, please!) to share with the rest of the AD's and show off shiny new distractions. So when you think of how the pieces are going to be used - that might give you a little more insight into what might make for a successful leave-behind. First off - it should highlight your art work. I struggle with names, but show me a piece of artwork and I can often remember an artist. So having a nicely designed business card is wonderful, but if it doesn't show me your artwork - chances are good I'll have no idea who you were, and the folks back at the office will have no idea what you can do unless they check out your site (good luck with that).