For all of these reasons, anyone interested in coffee must learn to taste. There is no traditional tasting ritual for the lay coffee drinker as there is for the wine drinker. Professional tasters, or cuppers as they are called, slurp coffee loudly off a spoon, roll it around in their mouths, and spit it into a bucket, which is not common after-dinner behavior. I suggest when you are tasting that you make coffee in your ordinary way, sample the aroma, taste some black, and then enjoy it. If you normally add cream and/or sugar, do so after the first sampling.
You may well want to compare samples of various coffees at the same sitting, however, so you have an idea of what coffee terminology actually describes. Remember that dark roasting mutes or eliminates distinctions in flavor, so make certain you taste coffees that have been roasted to traditional North American taste: medium to medium-dark brown, with a dry or vaguely slick bean surface. It is best to buy all of your samples from the same supplier, so that your palate will not be confused by differences in style of roast. You can either make individual samples with a small French press pot or a one-cup filter cone, or brew the way professional cuppers do. In either case, use the same amount of each coffee, ground the same and brewed identically.
I suggest you start with three coffees: a good Costa Rica Tarrazu (if possible a La Minita Estate Tarrazu); a Kenya AA, and a Sumatra Mandheling or Lintong.