In my experience:
- Be aware of the spectrum of people and businesses around you, it will help you develop the right connections
- A tradeshow always feels like a physical instance of a website to me - only sporadically I have made any true connections there
An advice is to show people that you want to work with them. At tradeshows, have pens and markers ready, participate in events where possible, do small workshops and demonstrations even if they are extremely simple.
- Participating in design contests and exhibitions, even if only partially related to your work, can be very fruitful in establishing connections and generating new business. See if you can talk to the organizers, they usually are the ones who know many people, including those high up in the organizations.
- Design a clever business card or give-away item, and spread them where you can.
- Let your contacts know you are there. Send New year's wishes, newsletters, and sometimes just call a contact to ask for information or advice about something.