The are so many different marketing, someone who need marketing strategies and started recently may become very confused. Since there are so many businesses that marketing is the most important factor, it's no wonder that getting confused and making many mistakes, especially in the beginning is a common thing.
People in business may disagree but one of the most important things that you should take into consideration that will make your business successful is your clients/customers. In the online casino businessmen for example, you can't afford to have a customer service mistake. It not only sums up to having a nice approach, the most common but disgusting mistake that can be done in business is giving the client/customer a V.I.P treatment BUT as soon as he or she hands the money there is no more respect, that's why I find it disgusting. Real-Estate agents unfortunately feel that they can afford to behave like this - once they receive the money(usually not a small sum when a customer buys a house) the behavior changes, that's why I insist that the behavior you give prior to the deal and after should remain the same, real-estate agents included. People can detect the change in behavior and in the next round they not only wont contact you, they will tell their friends and family not to come near and even publish online horrible things regarding your business, I am only talking about one person so far - you don't always know how valuable a customer/client can be, concluding the information I gave you so far - one very unsatisfied customer/client wont only prevent you from getting more money but can lead to damage and losses when your mistake was the change of attitude once his/her money was received.
Take good care of customers and clients even when not prepared to see them again.