In slower economic times, your desire to pull resources together is natural. Focusing your marketing on your strongest purchasing base, is a wonderful way to boost sales.
Let's say you don't know who your core clients are, then this is the time to find out. If you are new and do not have clients, focus upon those who your product or service will be best received. For example, if you sell medical instruments predominately used by surgeons and sometimes by general practitioners and others, you would want to dedicate 80-90 % of your time and marketing on surgeons. Don't ignore the 10-20%, just give it the right proportion of your time and marketing. Don't worry about missing the big pool of people. An organized, will thought out plan is better than one that appeals to everyone.
If you have been in business for a while, define and review who your Top 20-30 clients are. This would be your core group. What makes them similar? Narrow your focus to them. Develop your marketing strategy with this core group in mind. If you focus on this core audience, you will attract more people like them as this marketing will also resonate with others like this group.
Now that you have your core group, you can create offers that would appeal to these clients. Not only will you make these clients, who are most likely to buy your products and services happy, but you will attract more clients like them. Isn't that what you want more of? More of your reliable, purchasing core clients?