Just as in wine, one tastes beer to appreciate its qualities. One observes the color, the head, the aroma and the bouquet, the multiple aspects of its flavour, the aftertaste and so on.

The beer must be at its ideal temperature, according to its particularities, served in a glass corresponding to its style (no drinking from the bottle !), in respect to its density and its carbonation. The appreciation of beer also has its rituals, unfortunately all so often unknown.
Start by assuring that the recommended glass for the style of beer that you are about to savour is clean without compromise. If not, the dirt will be a nuisance to the persistency of the foam and will alter inevitably the flavour of the beer. Be sure the beer is not too cold, but at ideal serving temperature to appreciate it at its just value.