I used to get loads of 'free swag' when I attended the shows. I always found he best stuff was kept out of sight though, usually behind or under the booths....
So my 'Top Tip' would be to put a bit of effort into seeing what's hidden away, and you could leave with 5 or 6 iPhones, a couple of DSLR Cameras, purses & pocketbooks and more often than not, cold hard cash as well...
Like most things in life, the more effort you put into finding 'free swag' the more you get out of it...
