The First Session Rule
This is a simple rule, used after the first 'airing' of the character. If it doesn't work, change it! Any part of the character that the player finds he can not play, or that the DM finds he can not deal with in the campaign, change it to suit. Don't lumber yourself with something you do not like, and won't enjoy playing.
Lastly, plan the way that the players will meet, and roleplay the game with the individual player up to the point that they first meet.
Phase Two- Let's do lunch: Now the players have altered the unworkable bits out of their characters, and meet together for the first time. How this is done is up to the DM, but I believe conversation and conflict always make for a good start. The old "you meet in the tavern" seems a dreadful cliche, but it can be worked well. Have the characters feel each other out, and explore how their personalities intermingle. This can turn the banality of one of the more mundane parts of playing into an adventure in itself! Use the hooks from the character's background to entice the players into the adventure.
Phase Three- Up, Up and Away: Get on with the game, and enjoy yourself. Don't forget to make sure that the DM rewards players for good roleplaying ie. playing the character according to the template they have designed.
Every now and then, have the players re-read the background and character information that they first created. Do not feel the need to be governed by this information, but allow the character to develop into what you want. Roleplaying is all about having fun, and acting out the life of a character. People get bored of the same thing over and over again. To use an example from fiction, Luke Skywalker started out as a farmer, with dreams of going to the Imperial Academy. He went on to become a great hero of the Rebellion. His inherent capabilities and developing abilities changed, as did his personality with his exploits.
Let your characters do the same.