When I speak with a new client about their marketing strategy one of the first things I want to know is "who is your target audience?" Very often the answer comes back, "everyone!" That sounds like a good way to capture as many folks as possible, but it's actually not a smart marketing strategy. It doesn't allow you to identify the tools and vehicles you need to use to generate sales. For example, if everyone is your target there are a thousand different marketing vehicles you could use, but you'll be spending a lot of money to reach a lot of people who really won't buy your services, so you need to really get a good sense/picture of who you are targeting and who is most likely to buy your products or services.
So ask yourself, what does my best customer look like right now? Is it a man or woman? Teen? Small business, large business? Is it a family? If it is a person (rather than a business), how old are they? What else do they do? Where do they eat, where do they shop? How much money do they make? Once you start to answer these questions you can begin to look at the different but targeted ways to reach them. While some people believe Twitter is a social media tool to be used by everyone, it may actually be a poor way to reach teenagers, they just don't use it in the numbers that business people do. If you are trying to reach moms with kids, it might make sense to advertise on local blogs that appeal to those moms or on sites that offer activities to do with kids.
Give this a lot of attention before spending money on advertising and marketing so that your dollars are well spent, rather than just spent.