Users head to the site and see if anyone in their vicinity is looking for a share at about the same time they are. If no-one is, they post a departure point (where the cab will pick them up), a time of departure and a destination. The site supplies the user with estimated costs for the trip and suggestions of when to post requests (earlier works better than last minute). It also ticks down to the time of departure, so that the rider isn't late to meet his or her cabmate.
|(Photo by Josie Showaa)|
For those having trouble deciding which area to pick for a departure point, I'd suggest another website/app called CabSense.com which uses historical data on taxi routes to alert users to the best places to hail taxis.
I haven't yet heard from anyone who's used the service (apparently its available in cab-rich cities across the US), but I'm hoping to do so in the near future. I'll post my experience when I do.