Disrespect is a problem that, if not corrected in love early on in life, can have long term consequences. The best way to deal with a child's disrespect toward authority is to take the child aside, lovingly and yet firmly explain the significance of why disrespect is wrong and frowned upon, and if the child persists in this disrespect discipline should be applied. This is not to say that you are to abuse a child by any means; however, if the child is not disciplined correctly, the child could face many severe consequences in the future. As the quote goes, "Spare the rod, spoil the child." It isn't about beating a child here,  it's lovingly correcting the child before he ends up in a much worse situation.

1. Set a good example for the child.  Children are more prone to abusing or disrespecting authority figures if they have seen this being done by adults or peers around them. This is a passive way to deal, though.

2. Use positive reinforcement. Give punishments for those behaviors that are disrespecting while praise the child if he/she display the proper behavior. While spanking is considered barbaric and inhumane by some, it may be applicable to some children, especially if the children are willful.  

3. Be firm and consistent. The child instinctively understands that there are rules to follow and breaking them are a social no-no.  Set rules and go by them, even if it risks exposing you to answer that phone from a nosy relative.

If a child is disrespecting an authority figure outside of the home, it is usually a reflection of their behavior inside the home.

Be sure to be a firm parent, setting boundaries, sticking to consequences, and not letting their emotional outbursts effect your mood or attitude towards them.

When in doubt, I look to SuperNanny (the T.V. Show). She really knows her stuff.

Good luck!