What affects a drinks quality? This isn't going to deal with recipes and balance but the actual physical process of making the drink and factors that affect the guests experience when you make a cocktail. This is just a simple awareness to the seven factors that do affect drink quality.
#1 Glassware: The moment you put that glass on the bar and begin to create a cocktail to fill it, the glass takes center stage. Lip stick marks, hard water stains, chips and cracks can take this beauty queen straight of the pages of a magazine and turn her into a burned out drag queen. Fresh, clean glassware is a must.
#2 Bar Tools: I have worked with people that never rinse tins whether going from a vodka to a vodka drink or a mojito to a gin drink. Whether its laziness or the old, "The tins are seasoned.” Nobody want pieces of mint whether the guest or the bartender in their drink. That goes for muddlers which can tint a drink if not washed and going from muddling blueberries to grapes. Also, strainers, jiggers, bar spoons and pourers. Take pride in the tools you use.
#3 Ice: The masters have always stressed the importance of ice. Keep it clean. Frequently top it off. Keep bottles out of the service ice. While I would love to work only in places with Kold Draft ice machines, fresh cracked and shaved ice, ultimately, we have to work with what is given. Take into account that while you do need dilution to balance a cocktail some delicate flavors will get washed out when using smaller cubed or slightly melted (“soft”) ice.
#4 Spirits: I lived in a land of all bars being stocked with top shelf alcohol for bottom shelf price point until someone pinched me and I awoke with a tear in my eye. Ideally, we want to give the best and most expensive to our patrons, but beyond price know what you pour. Taste, read, listen, research both the standards at the bar and the new products that are coming out. Know your spirits flavors and nuances and how they mix. Plus, keep those bottles clean. Nobody wants to be poured a shot from a dirty, torn-labeled bottle that looks like its been sitting in a dump bin.
#5 Mixers: Whether juice, pop or even a splash of soda water, mixers play a key role in the make up of a cocktail. Fresh juices are only fresh if they are made that day before service. I even know places that batch out on the hour to maintain the freshest ingredient. Proper maintenance of soda guns and lines are crucial too, as not every bar uses freshly opened soda, tonic and pop bottles
#6 Garnishes: A drink is only as good as its garnish. Leave your slimy lemons and twists and brown edged limes aside. You can have the most spectacular cocktail but by giving it a worn garnish it takes away from the visual experience the guest has. Sight is part of the flavor experience. Also, keep those garnishes on ice. Why drop a hot bomb into a cool, peaceful drink.
#7 Smile/Flair/Presentation: Even on the busiest nights there is time to smile, just make it genuine. Over the years the skill sets of multi-tasking behind a bar grow with you. You would be amazed at the compliments that I get for even in the deepest of weeds maintaining a smile and having a quip for a patron. Imagine walking into a bar and ordering a drink. The smiling bartender shakes your hand and introduces himself/herself and grabs your name then proceeds to make a drink with flourish and serves it to you with a smile. Sounds great, doesn't it?