Entrepreneurs Brief Guide - How to Write Your Advertisement. Every start-up needs to spend some amount for advertising their business. Advertisements don't always have to be clever and witty, but can at times be subtle and straightforward. You must have a fair idea of why you are choosing to advertise, the thought process, where you will advertise and whether or not it will be effective. In 30 minutes, learn how to: (a) Target your customers, (b) Write an advertisement, (c) Position your advertisement appropriately and (d) Write a good advertisement.