The respect they have for you. And the respect you continue to show them.
If they don't respect you at this point it's highly unlikely they'll address you with polite deference. And ranting and railing about what a disrespectful kid they are, and how if you ever spoke to your parents that way when you were young you'd have been thumped, is not going to suddenly cause them to see the error of their ways and repent, forever after addressing you only with the sweetest civility.
This is very much a two way street.
Here again, it is you, the parent, who sets the tone. Speaking to them with polite authority through their earlier years shouldn't change when they hit their teens. If you continue to address them with courtesy and from a place of understanding, all the while maintaining a position of authority there should be no reason for them to suddenly begin addressing you with disrespect.
I've never been one who follows along with the way of thinking, that once kids hit their teens all bets are off. Neither in their behavior, promiscuity or in their manners. Why should a certain age give someone a reason to behave like an idiot.
No. Rudeness, contempt or sassing should be not allowed from young children and it should not be tolerated from your teen.
But now you can't send them to their room if they're rude. No. By now, you have to already have put the work in. Earning their respect in how they speak to you, by how you've always spoken to them. Showing them through example how adults deal with frustrations, conflicts or a difference of opinion.
And bear that in mind when your teen is speaking, voicing their frustration over rules they feel are unfair or holding a different opinion on any given topic is not rudeness or a lack of respect, it's part of growing up and separating from you. How they express these feelings and opinions however is what we're talking about.
This is not to say that if you set a good example and earn their respect, your teen will never sass you. They are teenagers. They are controlled by their hormones. They are going through a difficult phase of life. But as an overall tone. As an general rule, you and your teen should be able to maintain civility with one another.
Remember your teen is only a few years off adulthood. And if you're like me, you've always envisioned being friends with your children once they're grown. Bear this in mind when you're addressing them. Speak to them as you would to any other adult, resolve conflicts with them as you would with any other adult.
This is the time to begin laying the ground work for your future relationship, and believe me, as you pass through those years between childhood and adulthood, plain and simple good manners with one another goes a long way.