One thing that peeves me immensely is people who over promise but under deliver. One of the first rules of good business, especially when you're marketing services like we are in real estate, is that it's better to under promise and over deliver than the other way round. When you think about it, it's actually common sense. No-one likes to be let down, especially not one of your customers.
I am a firm believer in the practice of doing what it is that you've told people you're going to do. It's not actually that hard but it's amazing how many people make promises and then just don't follow through. If you tell a customer you're going to do something, you do it. And if you think you may not be able to do something, even if the chance is remote, don't promise to do it! Even if it's something small like making a phone call. If you promise to call back within the hour, do it, and if that may not be doable, give a more realistic timeframe.
This is where under promising and over delivering come in. If you tell a customer that you'll call them back tomorrow and you get back to them before the end of today, it makes you look like a competent, committed real estate agent. Your customer is also likely to think of you a lot more favourably for managing to do something sooner than you told them was possible. Under promising and over delivering also means no-one will be set up for disappointment.
Of course you shouldn't under promise to the point that it makes you look like you're doing a terrible job from the outset! Your under promising still needs to be realistic and acceptable, so when you do go above and beyond you look like a superstar rather than your timeframes appearing unreasonably long which may result in you looking lazy.