A player may gain up to 3 points from a given beer*. A minor difference in a beer (i.e. Potent Dry Beer, noticable honey flavor compared to Potent Dry Beer, Bold Honey flavor) does appear to be enough to get a point, but as your beer tasting goes up it appears that you're more likely to get points off of beers that are substantially different from what you've tasted before (i.e. Very Potent Sweet Brown Beer, hint of barley flavor compared to Dry Beer, hint of Orange flavor).
Beer Tasting is not taught at Schools. It is initially learned the same way it's improved: by drinking beer.