Something to do before your campaign starts.
Sit down with all the players and talk about the campaign. As was mentioned, outline your expectations for the campaign. If you want to give the players tons of freedom and expect them to be in the drivers seat, be up front and tell them that. OTOH, if you are running a more plot heavy campaign, you need to tell the players that too.
Create the party together. Don't tell the players, "Go and make a 7th level character and give me the PC's background." You wind up with an entire party of people that have absolutely no reason to get together other than they all have a big "P" stamped on their foreheads.
Have the group talk about things as a group. One thing I insist on is that every PC must have at least one meaningful connection to two other PC's. That way, you have the players come up with reasons why they are together. Have them build their backgrounds together and it makes things much simpler in the future.
As to the specific question of quest giving - again, this goes back to your first conversation with the players. Since they have come up with a group background, you know, or at least should know, what that group's motivations are. Play to those motivations. If the group is centered around some element, either threaten that element or reward it. Maybe this town that they are in is directly related to the backstory of the group. There, instant motivation. Maybe the group is more mercenary. Ok, pay them. Carrots work much better than sticks.