Often you will find that you are visiting distant cities just for a presentation, partner meeting or just passing through. If you happen to have a contact - whether it is a customer, lead, partner or industry mentor - you really should take any opportunity to just drop by and meet for lunch or even just a coffee. People tell you different things in real life from on the phone. Also, just meeting up is an opportunity for you both - after all you both have to eat, why not take the chance to squeeze out some business value as well at the same time.
It's that perfect chance to sell a few services days to ensure the product is working well, address any quick issues, find a new lead or just make that bond with your contact that much closer.
Recently I had a meeting like this which was just a last minute, "I-was-in-the-neighbourhood" kind of meeting, where we uncovered a quick opportunity that wouldn't have been thought of by the customer as a reason for them to contact us. The meeting led to a call to the right contact person, which led to a demo (and another chance to drop by for lunch) and a sale in rapid succession.
Some of this might seem like the basics, but doing some free product promotion or customer management instead of sitting alone at lunch is a very productive use of your time.
And even though you will usually shake out something that helps someone else in your team, it will still build your personal network and make you a more valuable resource for any company.