I agree with Hand of Evil in general here.
Booth babes are something that I'll look at when I see them, and perhaps even slow down my stride, but that alone won't pull me closer to the booth in question, nor get me to stay there longer.
Just having a babe at your booth isn't going to, in and of itself, drive up attendance. Nobody wants to be thought of as a gawker (even if they are staring at her), so they aren't just going to come closer to your booth to oggle her longer. Booth babes turn heads, but that two-second glance tends to be enough, so most people will just keep right on walking after checking her out, unless there is another reason for them to stop.
If you want something visual to pull people in, try something that's interesting in a more curious way. I remember seeing, last year, a guy in a dire-looking black robe walking around holding up a sign that said "The End is here. Booth ####". I almost immediately went to the booth listed to see what that was all about (turned out it was The End d20 RPG).
Likewise, personability draws people in. Having nice, friendly people in front of your booth to talk to people, show them things, answer questions, etc. is, IMHO, much more beneficial. People like feeling good, and friendly treatment does that much more effectively than looking at a sexy lady does (well, unless...well, you get the idea

).
Swag, by itself, tends to be something people just sort of expect at a big con like this. How much it draws people to your booth depends on what it is (and, maybe, how you give it away). Are you giving away buttons? A few people might slow down. Are you spinning a wheel where you can win anything from a button to a free book? Now that will make people stop and spend time at your booth. Likewise, discounts that rely on purchasing to begin with tend to be somewhat effective in getting people there to make a purchase, but doesn't necessarily draw in more people than you'd otherwise get (IMHO again).