Some of the shows I have attended I liken to Dale Winton's Super Market sweep. Hundreds of people grabbing and filling their bags with as many giveaway goodies as they can squeeze in. Worse still, I have witnessed the exhibitors themselves handing over their goodies without even asking one qualifying question. Businesses literally waste thousands of pounds each year supporting this practice.
You need to ask yourself : Am I sending out the right message here? Are these items really doing an effective job? Am I differentiating myself from the competition? After-all one pen looks the same as any other one mug or note jotter won't transform my business fortunes... who cares?
To help identify the right premium for your company, look at your theme and benefits message and link it to your main objective for the exhibition.
Your giveaway could be linked to your pre show invite eg something that is going to help your prospect solve a particular problem or educate them about your product. When your prospect has given you qualifying information about their specific needs or has participated in one of your presentations you can show your appreciation by giving them a reward.
Another idea might be to give away a redemption voucher that entitles the prospect to a free audit/report/etc. Make sure all your contact details are clearly visible your prospect needs to remember who gave them the gift. And don't leave items out on show for any one to take. This only weakens your objective and takes away it's exclusivity and value.