How do you deal during play with a player who makes things miserable for the others when he or she is not actively in the spotlight? Such miserable-making activities include frequently doing things in-game purely for the sake of attention that take time away from the other players, disengaging at the table when not actively at the center of things and needing others to catch him or her up on what has happened, drawing out anything that involves his or her character, and attempting to justify the attention grabbing by making bold, impulsive decisions in-game, steering the story in unwanted directions.
Last fall I ran a Pathfinder campaign that fell apart in large part because of one of the players demanding a disproportionate share of the attention and who would get bored and restless when not at the center of the action. The player did not realize the problem and truly wanted to be a part of the group; he simply lacked the self-awareness to correct his behavior on his own. I tried working with the player one-on-one outside of the game to no avail before eventually asking him to leave. It was understandably hard for some players to put the bad start behind them and the group disintegrated soon thereafter.
I am considering starting a new group in the near future and want to make sure that I do not repeat what happened last time if I get stuck in a similar situation