To fully appreciate beer, you need to put all of your senses to work: your eyes to see the color of the beer; your nose to smell the beer; your tongue to taste the beer and for mouthfeel; your ears to enjoy the sound of the bottle opening and pouring into the glass; and your sense of touch to feel for the proper temperature of the beer.
Most beers are best poured down the center of a clean, room-temperature glass. Many of the Belgian Ales are bottled-conditioned (yeast in the bottle) so you may want to decant the beer - pour the beer leaving the yeast sediment in the bottom of the bottle. Please use a glass and dont drink out of the bottle. Beer should be seen to be appreciated and the brewer spent a lot of time and money to create that beautiful head.
Appearance: Beer color can range from pale yellow, to golden, to copper, to amber, to red, to brown to chocolate to almost black. The length of time roasting of the grain determines the color of the beer. Flavor & mouthfeel can vary tremendously with beers of the same color.
Look at the head and size of the bubbles. Small, tight bubbles indicates natural carbonation. Whereas large bubbles often indicates artificial injection of carbon dioxide.
Many people consider a bright (clear & uncloudy) beer an indication of quality. I put very little emphasis on clarity - many cloudy beers are incredible.
Aroma: Pour the beer into the glass then hold it up to your nose to savor the aroma of the beer. You may smell the floral aroma given from the hops or the sweetness from the malted grains. You may also smell when improper brewing techniques or improper handling have occurred. Oxidation will smell like cardboard or metal. A skunky smell indicated that the beer has been light-struck or has been exposed to heat & cold.
Taste: Use all the the taste buds on your tongue. Sweet is on the front; tart/sourness at the sides of the back; and bitterness at the center back. Beer that is well balanced with give equal billing to all areas of the tongue. Not all beer should be well balanced. Some will be very tart. Some very bitter and some very sweet.
Mouthfeel: Feel the beer swirl over your tongue and around your mouth. A pilsner will be very light and crisp and a Trappist Double will be very full and tongue coating.
Enjoyment: Match the beer style to your activity. Playing tennis goes well with an American Pale Ale or a Lager. Smoking a cigar requires a Russian Imperial Stout or other robust ale. Properly pairing food with beer enhances both the beer and the food. Above all enjoy the company and conversation of the people with whom you are sharing the beer experience.
Responsibility: You know your limits. Beer should be fun, not tragic. Be responsible and know when to say when.