What to keep in mind while choosing an internet service provider?

I’m situated in a remote village and very few cable network providers are there in the area. But lately there are a couple of companies like Reliance, TataIndicom, Airtel who have broadband facilities.

I would like to go in for a low cost internet connection, as our internet consumtion is not much. I have LAN connections in several offices and each office has 5 PC’s approximately. Could we share the connection via LAN to all the PC’s? Each office will have a seperate broadband connection. Some offices would have a heavy load of internet useage. while most of them would be only cheching of mails and no major downloads done, except for updates.