What to look for
There are six categories to evaluating a beer with your review:

Appearance - Note the beer's color, carbonation, head and its retention. Is it clear or cloudy? Does it look lackluster and dull or alive and inviting

Style – What style of beer is it? Here’s a good link that gives insight to all the known styles of beer. Beer Styles (Credit: BeerAdvocate.com)

Smell - Bring the beer to your nose. Note the beer's aromatic qualities. Malts: sweet, roasty, smoky, toasty, chocolaty, nutty, caramelly, biscuity? Hops: dank / resiny, herbal, perfumy, spicy, leafy, grassy, floral, piney, citrusy? Yeast will also create aromas. You might get fruity or flowery aromas (esters) from ales and very clean aromas from lagers, which will allow the malt and hop subtleties to pull through.

Taste - Take a deep sip of the beer. Note any flavors, or interpretations of flavors, that you might discover. The descriptions will be similar to what you smell. Is the beer built-well? Is there a balance between the ingredients? Was the beer brewed with a specific dominance of character in mind? How does it fit the style?

Mouthfeel - Take another sip and let it wander. Note how the beer feels on the palate and its body. Light, heavy, chewy, thin / watery, smooth or coarse? Was the beer flat, over-carbonated?

Drinkability - The beer's overall ease of consumption and your overall impression of the beer. Would you have another?