If Google adwords is working for you, why not keep working on that acquisition method? Do you have a Dribbble account? Could be a good source for new customers, too.

When looking for a logo, clients want to see your past work, hear recommendations from your customers, and know the pertinent details (how long will this take, what's the process)? I find most graphic designers make this all hard to find on their websites, so make sure you are optimized to answer your customer's main questions before they have to ask them.

If you don't have time for your own blog, there's nothing wrong with that, but perhaps you could write a guest post for another small business blog that gives tips on picking a designer, communicating your vision to a designer, what to expect when you want a new logo, etc.