One of the single most important things in business is marketing - and one of the main reasons a lot of businesses fail is that the people running the business don't have a clear understanding of their market.
The first question you should ask is "who is my market?" The answer is not "everyone".
Your market is not "everyone" unless you're a huge corporation with millions of dollars to spend on marketing and advertising AND you have a product with a wide appeal. You can't be "all things to all people" so the first thing you should do is pick something specific. The more specific you can be, the better you can tailor your marketing to that group. For example, "women" is way too general. "Single mothers" is better but "professional single mothers over 30 with toddlers" is even better. "Athletes" is too general; "golfers" is better and "retired men that play golf for recreation" is even better.
Pick a niche. The tighter you can niche something, the more likely it is that you'll make money. If you target people in a very specific group, they are likely to feel as if you're speaking directly to them. Think about it: if you're trying to sell digital cameras to "everyone", you have to compete with the thousands and thousands of other businesses that sell digital cameras. If, on the other hand, you're marketing a special tripod to ornithologists for taking photographs of small birds, then the competition goes way down because you're one of the few people offering that to a specialized market. Generally speaking, the more "niched" or specialized you are, the higher the prices that you can charge.
Give them what they want; not what you like.
I have a friend who hates golf, but he makes a ton of money on the Internet with sites about golf.
Things to consider: age, gender, income and education level, single/married/divorced, occupation and ethnicity. "Psychographics" are also important, which are things like values, attitudes, interests, behavior and lifestyle.
Get clear about the features and benefits of your product or service.
People are usually more motivated by the benefits. Think clearly about what benefits would motivate your customers to action. When you're writing copy or speaking about your product or service, focus on the benefits.
Try to visualize a specific person that is your typical customer.
This can make it easier to write your sales copy because now you've got "someone to write to", rather than a nebulous idea about a "market". Study the marketing of other companies - from the big corporations to small businesses. Notice what's effective. What marketing techniques used by other businesses or markets may be applicable to your business?
Pay attention to what motivates you, but be aware that different things may motivate others. Finally, read everything you can get your hands on about marketing. The ability to market effectively isn't something we're born with. It's an ability that develops with practice. Only by paying consistent attention to this topic will your efforts improve over time and hopefully result in the one thing that really matters: sales.