Parents often engage in nagging techniques because they need their child to do something and because they believe their persistent requests, demands, reminders, and threats of negative consequences will influence them to do what they want. What most parents fail to realize is that even when nagging does work, it usually ends up leaving both sides with negative feelings about the whole matter.
It's really important to understand how nagging affects everyone involved. For one, nagging says to your child that they're either unable or not responsible enough to do what you've asked of them without being reminded. It may be true, but what happens is kids will start to internalize this belief and live up to the expectation that they are irresponsible. They begin to believe that they can't do it rather than they won't do it. The other thing about nagging is that it sounds more like a demand than a reasonable request. Demands are inherently inconsiderate because it tells the person that their feelings absolutely don't matter. It's also very disrespectful. You're effectively "pulling rank" and making them feel powerless and inferior. Imagine having a superior at work demanding rather than requesting something of you, and you should understand what negative feelings this might bring out in your child. Rebelling becomes a natural reaction. Finally, nagging can give your child a false sense of power because they learn they can make you upset and amplify your nagging to ridiculous levels by holding out. The longer they wait, the more powerless and upset you feel because your words continue to lose influence on your child. You react by nagging some more, which causes them to wait even longer, and the vicious cycle goes on and on.
There are a few things you could do in the place of nagging that might benefit everyone involved. The first is to come to a reasonable agreement on what needs to be done and when. Make sure that an understanding of the consequences is communicated clearly but gently and be prepared to follow through with those consequences if the agreement is not met (which will likely occur often at first). Many kids will make agreements too easily just as a way to postpone what needs to be done. They may also get defensive or upset even at a simple request. Rather than reciprocate the negative attitude, make it easy for them to discuss their objection so that an agreement can be made. Once you've come to an agreement, resist all urges to hint, remind, re-ask, or demand. This is hard for some parents to do because they actually fear what would happen if their child does not come through for them. This could range from something as minor as the dishes sitting in the sink longer than they should to not filling out college applications before the deadline or taking their medication. The fear or frustration may be so strong that parents will either give in to the urge to nag or end up doing it themselves. This is probably the worst thing you can do since all it does is reinforce the irresponsible behavior and teach them that they can get out of responsibilities by just waiting long enough. Instead, be patient and show that you have confidence in your child even at the risk of them not coming through. You may be surprised.