Engage with your customers

Stay up to date on your market.
Research your industry regularly to stay up to date on all new innovations, develop price/competition sensitivity by doing proper market research

Use the “pull-and-stay” method
Pull customer information by taking visitor’s email addresses. Stay in front of them by providing information about your services. Send them an email to say thank you for coming and ask what they thought about the event. Start a conversation. Engage with them, get to know your marketplace. You'll be amazed at the responses you receive.

Use social media to get knowledge, to stay updated, and to build social currency
Send out ads and blog post updates on Twitter, run a fan page on Facebook, hunt down potential customers, and try to pitch to them through LinkedIn.

Avoid spamming.