Writing skills questions

[sapphire_chan]

Okay, I've started, and I'm running into a stupid problem, so I thought I'd ask you guys:

How do I keep all my characters from sounding like me?

[allgirls]

I imagine them all out. I base them on other people and I write notes about their motivations etc. Their backgrounds that might lead them to make certain life choices etc. Index cards with their names and their descriptions help.

I pick them up and put them in their situations after I've fleshed out their character somewhat.

[sapphire_chan]

I've got a characters document started already, cool to know that experienced people do that too.

It's not so much what they're saying that's the problem as how they're saying it. It sounds like it's coming out of my mouth. And how I talk/write (e.g. letters) changes depending on what I've been reading so I have this horrible vision of every book I read making all the dialog shift.

It's a cadence and pacing problem not a content problem, if those are the right words to describe it.

(Although, since Agatha Christie has a whole book where everyone talks about "certain" things which lead to "certain" results maybe it's a really common problem to have everone sound the same?)