Is this a well known and well attended event in my industry?
Will the cost of attendance be potentially covered by the resulting business?
If you're not sure, do some advance research. Take time out to visit the event before booking your stand for the following year.
Talk to the organisers about who attends, who exhibits, what information will be available to you, what advertising and promotion THEY are doing to promote their own event.
Also talk to those on the stands. Find out from them how useful it is – what is their objective for being there, do they feel it's achieving that.
If you decide to exhibit, publicise your attendance at every opportunity. Let your customers and prospects know you're going to be there, and what they will gain from visiting you.
For example, if you're launching a new product, tell them what it can do for them.
Put it in your email signature, together with your stand number.
Drip feed it on social media in the weeks leading up to the event – but don't just say you're going to be there. Give them reasons to visit you.
Make extra efforts on social media to connect with potential new customers.
Look for discussion groups or hashtags discussing the event to see who else is going or interested.
See if there are opportunities to appear on the organisers website or the event website with a link to your own website.
Use email to communicate with your potential customers – if you can access a database (e.g. from the organisers) so much the better.