I've tried over 125 different coffees and I'll explain how I choose.
First, I think about the country where I want my beans from. There are general characteristics to countries with a lot of variation among specific estates and roasts. Indonesian coffee has an earthiness. Costa Ricas are clean and mild but have some nice bright 'high-notes' like citrus and berry flavors. Colombian coffee is famous for being well balanced, with good body, brightness (body) and flavor.
Personally I love deep rich earthy flavor in my coffee.
So I often choose something Indonesian or African. The equivalent for me is when I'm drinking beer I prefer Guinness or a strong ale like a Porter Ale. In the morning, I have my first cup of coffee and my tastebuds aren't yet awake so I need that extra bold earthy flavor. So anything from Java, Bali, Papua New Guinea, Kenya, Ethiopia, etc. is perfect. I know that coffee pro's would say that all those coffees taste different, but to me I like the variety within the general earthy-bold-molasses-caramel range.
I find that dark roast brings out a lot of that flavor. An example if anything from IronBrew. It's like having a galloping horse in your coffee cup. Tons of flavor, boldness, molasses. Due to being from the Cerrado region of Brazil and also a dark roast.
If I'm splitting hairs, I'll try a coffee that has been dry processed because it will have a wider range of deeper flavors because the beans were dried with the coffee fruit still on it, giving it some additional flavor. You won't find dry processed beans being used at Starbucks, Peet's, or your local supermarket brands. The reason is that their suppliers use wet processing because the fruit is immediately taken off the bean and the beans float off -- and it is easy to determine bad beans that need removing. But some people say wet processing sacrifices flavor. I like dry processed beans because they've dried in the shade, under a tree, on a tarp, on a screen...something more natural.
Sometimes I'll have a blended coffee because I like the consistency and broader flavor profile. Coffee can be blended by country (Kenya AA or Tanzanian Peaberry, for example), by region (IronBrew's Brazilian Cerrado-region coffee, for example) or by a specific town. But just like blended wine, blended coffee like the kind from Rogue that I reviewed recently give a consistent flavor. And a blend can provide a broader flavor profile than any single estate or country bean. For instance, Rogue's blends have earthiness that I assume comes from one kind of beans (Indonesia? Ethiopia? Dry processed?) but also some lighter citrus flavor that might come from a different coffee (Costa Rican? Colombian?). I like that broader flavor.
Aficionados might prefer single estate coffees for the same reason wine connoisseurs like single estate wines: they get a distinct flavor and can associate it with a specific farm. But that's not for me, at least yet. I like a bold, rich, dark roasted cup!
How do you choose coffee? Enter it in comments below!