Call to action is a part of the sales letter that compels readers into responding positively to your sales pitch. Believe it or not, people need to have a reason to make an action. It seems that Isaac Newton's First Law of Motion, which states that an object will stay in motion or at rest unless an outside force acts on it, also applies to human beings. People are usually not compelled to buy or do something if not triggered or provoked. Thus, a call to action is essential in making a successful sales letter because it is helpful in sealing the deal.

In order to grasp the meaning of call to action much better, you should put yourself in the shoes of the customer. Basing from your experience, what made you call the number on the TV screen to purchase the exercise equipment that is already accumulating dust in your garage or basement? What made you apply for a subscription in a women's health magazine even if you are male? But simply hearing or reading the word "buy now" is not enough to convince someone to purchase anything, especially one who is skeptical or undecided.

In order to make your call to action effective, you need to create a sense of urgency. Tell your readers or prospective customers that they should act now, otherwise they just won't. For example, tell your readers that there are only 100 product units left or a 40% price cut is good for callers within the next 30 minutes. Remember that if people do not act (or buy) immediately, there is a big possibility that they may never act (or buy) at all. Using words such as "limited offer" or "only valid within the week" will surely make someone want to purchase immediately so as not to miss the opportunity.

Another tactic to compel people to act immediately is to give them a reason to do so. Tell them the additional benefits of buying your product. You should tell them, for example, that if they buy now, they would be given a free gift or that the delivery is free. It may also be effective to tap on people's desire to fit in by saying "don't be left behind" or "your neighbors probably already know about this special offer". If you are still unsure of what words or phrase to use to make prospects want to act right away, there are a lot of resources online, such as books, CDs and articles that can help you come up with a call to action.