There are many things you need to do if you want to make, keep and grow your business relationships, but the most important tasks that lead to success are all in the follow up.
Just because you met someone and exchanged business cards does not make them part of your network. In fact, it is this misconception of "instant friendship" that soils the whole concept of networking. It takes time and an ongoing effort to cultivate real connections.
My friend, Bruce Allen, had some interesting advise on his blog recently under the title: "Developing Face-to-Face Networking Skills :: Idea #7". (His other six ideas are good, too!!)
His advise is to select only three business cards from people you meet at any event and follow up with them in three different manners. Person one gets an email, person two a handwritten note, and person three gets a phone call. While I always prefer the idea of sending a handwritten note (because it takes the most effort and will stand out more than an email or phone call), Bruce's idea is great because it makes the process less monotonous, and thus you are more likely to do the follow up. Sending three handwritten notes is a chore, but one email, one note and one call will be perceived easier and more fun (nobody likes to do the same task over and over).
The other reason this idea is intriguing is because you can track your methods of follow up, eventually discovering a pattern of what is working best. If you end up having more follow up meetings (and building closer relationships) with those who get a call vs. those who receive an email, you will soon learn to use the phone as your preferred method of making contact with new people.
However you decide to follow up, just do it. Without follow up, you will not develop a real network.
Have A Great Day.