Taken from the Ballast Point site....
Tips on Tasting
Here are some points to keep in mind if you are getting set to do any kind of serious beer tasting.
Baby your taste buds. Palate preparation is all too often neglected in beer evaluation. The taste buds and aroma receptors are complicated instruments that need to be in prime condition to properly identify the myriad flavors in beer. Spicy, acidic, or thermally hot foods and beverages can all do temporary damage to your taste buds. Smoking will also deaden the taste buds. Optimally, you should guard your taste buds carefully for a full day before you plan on tasting. Similar precautions should be taken to maximize your olfactory capabilities. Aftershave, cologne, or perfume will interfere with your ability to detect subtle aromas. And if you have a head cold, it is advisable to forego the tasting session. The aromatics in beer normally have to penetrate a thin layer of mucus to reach the olfactory epithelium, but having a cold thickens this layer and reduces your sense of smell.
Examine the bottle. Serious tasters will examine the bottle and its contents with a flashlight. The sediment should be tightly packed, but may have been disturbed in shipping or by the steward. A ring around the inside of the bottle near the fill line sometimes, but not always, indicates a contamination. This should be noted for future troubleshooting purposes; keep in mind, however, that a ring may also be formed by nonbacterial means. Similarly, beer in clear or green bottles may become lightstruck with improper storage. Although these bottle conditions are useful troubleshooting tools, it is important not to let the power of suggestion lead you astray -- let your taste buds, not prejudice, be the judge.
Pour the beer properly. Pour the beer down the side of a glass held at an angle, taking care not to disturb the yeast cake in the bottle. Gradually rotate the glass to an upright position and finish in the center of the glass. These steps will ensure sufficient, but not excessive, head foam -- usually one to two inches. In judging, all beers in a flight should be served in the same manner to keep them on equal footing. In addition, it is important that the beer be served in clean glassware. Sanitizer residues can mask or interact with compounds in the beer and interfere with head retention.
Check the initial aroma. Immediately sniff the beer upon pouring because many aromatics will dissipate quickly. Just a couple of normal sniffs will suffice; too much sniffing can lead to olfactory fatigue, which would require a 20-second or so wait for adaptation.
Check the appearance. Observe the color, head, and clarity of the beer, noting their appropriateness for style. Well-conditioned, all-malt beers generally have dense, tightly packed heads with uniformly sized bubbles. The minimum standard for head retention is a half life of one minute or so; that is, the froth should take no less than a minute to fall to one-half its initial height.
Check the beer's steady-state aroma. Sniff the beer again, noting any components that have appeared or disappeared. The aroma will generally be less lively, but the background malt and hop character should be perceptible.
Now you get to taste the beer. Take a small sip and note the initial, intermediate, and final tastes. Most beers have an initial maltiness that carries throughout the flavor until it is attenuated to different extents by the hop bitterness. Flavors that result from esters, hops, and aromatic compounds will generally be perceived in the middle of the flavor, while the aftertaste will be the sensation that lingers in your mouth. Be sure to swallow the beer to allow the hop alpha-acids to flow across the bitterness receptors on the back of the tongue. Take another sip, swishing the beer through your mouth to evaluate the temperature, carbonation, viscosity, and alcoholic warmth. One or more additional sips may be required to identify subtle flavors, but most beers can usually be properly identified by imbibing two to three ounces.
Evaluate the style. Reflect upon the beer, considering its positive and negative flavors and how close the beer matches the style and/or your expectations. In beer and wine tasting, the overall impression is often more or less than the sum of the parts, but in any case, a good tasting experience should make you want another.
Cleanse your palate. In most tastings, water, unsalted crackers, and/or bread are usually available to help absorb and rinse flavors in between beers. Keep in mind, however, that this introduces different chemicals into the mouth, which may in turn affect the next beer. Any solids should be thoroughly rinsed with water before you proceed to the next beer.
Some Common Flavors Found in Beer
Descriptor Perception Synonyms Comments
Acetaldehyde O,T Fresh-cut greenapples Precursor to ethanol in fermentation, sometimes
found in young beer; may
be formed through the
oxidation of ethanol and
further oxidized to acetic
acid; may also be
produced by
Gram-negative bacteria.
Astringency T,aT Mouth-puckering,
grape skins, tart A mouthfeel that results
from compounds that may
be:
1) Produced by bacteria,
in which case it is usually
accompanied by other
off-flavors.
2) Produced by wild
yeast, in which case it is
usually accompanied by
phenolic flavors.
3) At elevated levels
because of excessive
hopping or extraction of
polyphenols during the
sparge.
Cooked
Vegetable O,T Cooked corn,
celery, cabbage,
parsnips Associated with sulfur
compounds such as
diethyl sulfide and
dimethyl sulfide; produced
from malt precursors
during the wort boil and
cooling; high levels may
be produced by
Obesumbacterium
proteus and enteric
bacteria.
Diacetyl O,T,aT Buttery,
butterscotch,
slickness Vicinal diketone with a
threshold of about 0.1
ppm; is reduced to some
extent by yeast but may
be at elevated levels if the
beer is prematurely
separated from the yeast
or if the respiratory ability
of the yeast is impaired;
also may be produced by
lactic acid bacteria, in
which case it may also be
accompanied by sour
flavors.
Estery O,T Banana, fruity,
apple or pearlike Produced from acids and
alcohols; levels may be
elevated because of the
yeast strain, high
fermentation
temperatures, high-gravity
worts, low pitching rates
or long periods in contact
with the trub;
accompanied by
solventlike flavors at high
concentrations.
Grassy O,T Fresh-cut grass,
leafy, haylike Usually associated with
an aldehyde called called
cis-3-hexenol, which is
formed in malt stored
under poor conditions.
Similar flavors are derived
from the oxidation
products of humulene in
old hops.
Papery O,T Stale breadcrumbs,
cardboard The result of staling
aldehydes, primarily
trans-2-nonenal, which
are formed from the
oxidation of higher
alcohols when beer is
exposed to oxygen or air.
Phenolic O,T Medicinal,
plasticlike, smoky,
adhesive strips Aromatic hydrocarbons
produced by yeast,
particularly wild strains,
but are also associated
with coliform bacteria;
these compounds may
also be extracted from
malt, hops, and sanitizer
residues.
Solvent O,T,aT Lacquerlike,
acetone, warming Associated with high
levels of esters such as
ethyl acetate and isoamyl
acetate; these
combinations of acids and
alcohols result from high
fermentation
temperatures, high-gravity
worts, low pitching rates,
or long periods in contact
with the trub.
Sour O,T Sour milk, not to be
confused with acetic
acid The result of lactic acid,
which is produced by
lactic acid bacteria;
detected as a sour
sensation on the sides of
the tongue; acceptable in
some styles, but
generally indicates a
sanitization problem; the
growth of lactic acid
bacteria is inhibited by
high hopping rates.
Key: O = Odor, T = Taste, aT = Aftertaste