Once you start to network, you will accumulate a ton of business cards which are a pain to maintain. What I do is follow up by sending mail to each person I met the following day - don't leave it more than a week or you will end up not following up. if a person replies, it shows they are interested in maintaining a relationship and once their mail comes in, their name and address is automatically added to your address book (for Gmail). What you can do then is to use the address export function in
LinkedIn and add that person to your list of business contacts. I can use LinkedIn to manage my business comrades by region and can see who they know and as for introductions if needed. Its also much better than managing your contacts through physical meishi which you can simply search.