Do you ask for referrals?
I was thinking about this late last year but perhaps you could say it's a bit of a new years resolution. It's a simple tactic that many people forget about or are to shy to do.
But I think it's a hugely valuable habit, and one I'll be practising this year.
At the end of every meeting with current or potential clients just ask them;
Is there anyone you know who would like a call or a coffee to chat about [insert whatever you do here]. Would you mind making a quick intro?
Get one or two names and when you're back in the office search for them on Twitter, LinkedIn and Google etc. Add to your network and follow them so you're listening for nice opportunities to connect and engage. Then when the email intro is made you'll have a head start and be in a great position to build rapport.
If you're doing this already please leave any other suggestions or experiences you have to improve this tactic.