Less information to begin with usually helps them to concentrate on the immediate choices to hand rather than worrying about the world at large. The worst trait that players can exhibit is that of the "Setting Lawyer" where they bring their own knowledge of the world, gained by playing other scenarios, into play. This can be a real problem for DMs who are not as familiar with the setting as some of their players and can be very disruptive or diverting for the rest of the group, particularly if conflict between player and DM arises as a result.
|Chaucer's Pilgrims - The Canterbury Tales|
Gary Gygax's sage advice on the subject (A&D Dungeon Masters Guide, p. 87), which is interesting to read nonetheless, seems to be aimed at DM's running their first campaign and perhaps at novice players.
I entirely agree with Joe that the first few sessions of any campaign are really spent getting to know one another and less about finding out where in the world they are or what their next move should be. Starting of with a simple scenario to get them used to each other's company, traits and talents is a must.
When running my own campaign world my objective is as much about developing my world as it is about playing out interesting plot lines. To help me achieve this goal I insist that the majority of players select lands other than the starting location as their PC birthplace. This often requires them to come up with a convincing reason for embarking on some form of quest as part of their background, giving me the opportunity to weave parts of this into the arc plotline (clever, yes?).
I also recommend that DMs run short solo encounters, as prequels for each PC as a prelude to a campaign. These do not need to be any more than 30 to 45 minutes each and can usually be done as part of the first session or offline if needs be. Your players will thank you in the long run as it bridges the gap between character creation and provides believable reasons for turning up at that cliche of a tavern looking for work.