The registration bag was stuffed full of promo items, 80% of it paper items. Many authors had multiple pieces of "paper" in the bag. Paper items include bookmarks, postcards, sheets of paper.

I pull out things that catch my eye, but the rest goes in the hotel trash.

By this I mean, don't stuff it in a bag that everyone gets, but make it available for someone to choose to pick up, whether it's on your table at a booksigning, at a workshop, or in the spot the conference has assigned for promotional goods. That way you know they WANT your paper item, and are going to at least look at the information before tossing it.

One thing about promo items--will the person who's getting them be able to use them in their house or at work, without worrying about their kids or boss seeing them? 

Nice pens for me are those that don't look cheap, like the examples here. 

Again, if it's too blatant and sexual, or otherwise inappropriate, it's not going to be useful to anyone with a family and it will probably get tossed. 

You'd think books in registration bags are a great promo item, but in fact I know many people either take theirs down to the promo item table, or simply leave them in their hotel room. 

If you're going to do a promo item like candy, make sure it's marked. And realize that few people may even pay attention to your identifying info before they separate it from the candy! 

In other words, it's better when the item is permanently engraved with your info, not just on an outside wrapper or something else that can be removed from the item.