well, Chelsey will be 17 in October and the path we've taken with her is that she shouldn't speak to anyone (adults, friends, other children...anyone) in any way/tone she'd not want God to hear
If she does start with teen attitude I usually firmly but gently remind her that she professes faith in God and therefore needs to act accordingly. It usually works. She is also often reminded that snapping at others is usually an indication she is upset about something else or with herself and that she should think before she speaks. Of course our lives are also based in natural consequences in discipline so if she doesn't act in love with us, she doesn't receive our gifts of love in return (ie. rides to her friends homes, the mall, extra spending money etc) so that helps
lol
My 6yo recently was disrespectful to me in front of a friend - she yelled at me :ack when I asked her to please not open the refridgerator as we'd be eating dinner in 15 minutes. she yelled "but i'm hungry NOW!". I gently but firmly told her she needed to take a moment in her room to calm down and then she could come out and apologize to me and my guest for being so disrespectful. Its hard but I think if we're consistent when they're younger it will be easier (i hope) when they're older.
Chels is easier then many teens I know when I just remind her , adult to adult(sort of) that she needs to remember who she wants to be, how she wants to live and that her acts toward others reflect directly her relationship with God