Whenever possible, and when a player seems interested, I try to run a short mini-adventure for each character before the main campaign gets started. In this mini, you can set-up the character's reason for being an adventurer, this reason being shown by actual play as opposed to related background. I find it tends to make the player relate to the background more, since the events have been experienced rather than just described.
This method also works well for pairs of characters that already know each other. It also allows for the introduction of special items into the campaign. In this way, a character can start out with some item he/she earned in an adventure, rather than was given as background. To me, this makes the item much more special. Also, it is guaranteed to go to the character of your choice, as opposed to the character of the party's choice, if that makes sense to you.