Look into pitchmen. Joel Bauer started as a pitchman, in which he used his magic act to get attention for his client's booth. He understands that the unexpected and entertainment are big factors of attention.
Giveaways...hey, it's possible to give away a lot of things and not get anything in return. Build a feedback loop into whatever you give away: if it's a contest, make sure they have to log into your site to see if they won, for instance. Or call you. Then you get another chance to communicate with them. Match the giveaway to the theme and audience. Giving an iphone 7 away to a crowd at a power generation show isn't a great fit and isn't memorable.
I've heard an example of co-opting other people's booths. This is interesting because you expand your distribution channel at little cost. The idea is you ask if you can put your brochure on their countertop, and in exchange you'll by their crew lunch. Of course this works best when your products are complimentary and not in competition. Imagine if you got 4 or 5 of these to work with you. "Everywhere" the attendees go, there's your brochure. You must be legit.
But the key thing is: make sure you get the conversation AFTER the show is over. Collect business cards; screen a little for fit; book the next conversation. Don't try to do everything at the show. Yes, it's possible to set up big deals right there; however, you probably won't and your objective should be to get awareness of you and your brand into your target market's (distributor's) head.
Or run a theme to your stand. We got an accounting firm to dress up as "Jack and the Beanstalk" characters and they walked round the whole show interacting with visitors and being photographed.
Everyone came to the client website to see their photos with the Giant afterwards..... where on the same page an offer was made.... Cute, engaging and very simple to put into practice.
http://lovetogrow.co.nz/annual-accounts/ is the offer page!
Begin by putting yourself in your target audience's shoes (aka: the shoes of the people attending the trade show.) What would surely get their interest? What types of benefits are they looking for in products/services? Are these people with a good sense or humor or are they looking for awards, approvals and things like that to verify a legit product/service in your industry? Once you understand what is attractive to your customer base, then you can start coming up with ideas.
These ideas could range from just designing an excellent exhibit space with documents and posters that display all of the information/benefits that this audience is looking for, to a social media contest/conversation with a hashtag.
Having experience with trade shows, I would definitely suggest you pre-order promo items that your audience will find interesting - if you want to be out of the box, then my suggestion would be for some sort of puzzle to be solved. Something that people would have to move around or use critical thinking skills to accomplish, and then inside could be an item of importance or something like that. Or you could even hold a contest at your booth in which different companies work in teams to compete against each other to complete a task or solve a puzzle or something like that.
Turns out this is kind of difficult to explain via writing. If you'd like more ideas or any elaboration, please contact me! You can contact me on Clarity or you can contact me through my website: www.bloominari.com (I own a marketing agency). I love helping businesses solve problems and engage their audiences, so feel free to reach out to me!