1.     Here's a rule of thumb. When a liquor bottle outfitted with a medium-speed commercial pour spout is inverted between 45˚ and 90˚, it will dispense approximately 1/2 oz. of spirits per second. Based on that, an internal cadence of "one-one thousand, two-one thousand, three-one thousand," will yield a 1.5 ounce portion of spirits.

2.     Should the count of three result in more than a jigger of spirits in the glass, then the bartender's internal cadence is too slow and will need to be sped up. If there's less than a jigger in the glass, it means the person's cadence is too fast and will need to be slowed down. After that, it's just a matter of the bartender maintaining a consistent cadence.

3.     Liqueurs, which are denser and more viscous than spirits, will pass through a spout at a slower rate, which means that when free pouring Baileys or Kahlúa bartenders need to know to compensate by counting more slowly.

4.     It's advisable to routinely test bartenders pouring abilities. Arrange a half-dozen empty glasses on the bar rail, and have them quickly pour a staggered series of measurements into each. Afterwards, pour the contents of each glass into a graduated cylinder, or measuring cup to gauge their accuracy. Many operators establish standards for pouring accuracy, and if a bartender doesn't pour up to those standards, the individual is required to use a shot glass until such time as he's able to consistently free pour accurate measurements.