Due to the evolution of modern media I prefer to depend on exposition through dialogue. I try to avoid *telling* the reader anything. With simple plots this is easily achieved (often through the romantic sub-plot):

A meets B. The characters are new to each other and therefore disclose a plethora of information; backstory, likes, dislikes, hopes and dreams etc.

With more complicated, multi-character plots this becomes troublesome: 

Karen and Cindy are besties: they know virtually everything about each other - they've know tales to tell. Subsequently, I introduce a new character, Lisa. We can now learn 'everything' about Karen and Cindy because they need to bring Lisa up to speed. The problem this method creates is that Lisa is new, shiny, and features in the majority of scenes.

Lisa's domination can cause the reader to believe that she is the main character. My 'goto' method of dealing with type of character is simply to kill them, afflict them with some terminal illness, marry them off, get them fired, or otherwise despatch them.

Anybody got any better ideas?