Mead utilizes a range of yeast for its fermentation.
In modern times many mead makers use the same types of yeast as one commonly sees in winemaking, much due to the commonality between the two beverages.
Using Specific Gravity to measure sugar content, both before and during the fermentation process, meadists can calculate alcohol ABV%. This is often done by use of a refractometer or hydrometer.
By measuring gravity, a meadist can also quickly notice stuck or sluggish fermentation, and by that make the appropriate corrections.
Mead will generally ferment the best when one follows the instructions from the yeast manufacturer.
Primary fermentation is said to have reached its end when “bubbling” ( through airlock) has slowed down significantly, or when gravity is approaching target gravity. It should then be racked into a new vessel. This is referred to as racking to secondary.
For more advanced meadists there is a workaround; by using conical fermenters. These fermenting vessels are designed with a cone in the bottom, which collects lees and yeasts. In the tip of this cone is usually a ball-valve or similar. This valve allows for tapping out yeast and lees at end of fermentation, and allow the mead to have both primary and secondary stages completed in the same vessel.
Lately hobbyist meadists has also gotten access to such conical fermenters through the development of fermenting vessels such as The Catalyst, FastFerment, and the Fermentasaurus.