<font color=navy>Some advice that someone gave me once -
Talk to your children - don't spank them. Teach them with positive reinforcement. But .... if you do spank them (as in punish - not anger), spank them hard so they never forget it.
That was a nun who said that & it made me laugh because it was so unexpected, but I think I agree with her.
My ds came out with an attitude when he was 11, and I spanked him three times very hard with the belt, and I told him if he EVER talked to me like that again, I wouldn't hesitate to spank him again - without hesitation - even though it was not something that I liked to do. You know, he's never ever used that tone with me again, and I've never spanked him again. When he comes out with an attitude, a simple talk usually does it. My dd is the same way - she's more moody, but she doesn't show disrespect (at least to my face). When she was 12 she came off with an attitude a couple of times in front of her friends, and I had a talk with her -- it hasn't happened again. I'm lucky I think.
One thing I do, though, is I don't make a threat I can't follow through with - I don't make a threat that I regret. The kids know the consequences, and 9 out of 10 times I follow through with them. Sometimes, though, I do back down after talking things over with the kids (they're ds-15 and dd-14 as of yesterday)
Good luck with the attitudes - it's not easy raising kids, and harder to know what the best thing is.
Last Friday, my ds & I went to the mall, and he was criticizing some stuff I had done (getting too involved), and I told him that he was not free to make some of the comments he made. He said, "well, as equals..." And I had to tell him that we're not equals - I'm his mother and he's my son - therefore, we are not equals. His eyes got teary. That was hard for me because I'm so close to the kids, that the parental/child boundaries sometimes seem to blur.
I'm rambling.

Good luck w/your own rascals.