You make a Dexterity check when you roll for initiative. (90)
The Acrobatics, Sleight of Hand, and Stealth skills reflect aptitude in certain kinds of Dexterity checks. An individual proficient in one of these skills adds his or her proficiency bonus to ability checks that involve the skill. Without proficiency, the individual makes a normal ability check.
¹ Roll 2d20 if you have advantage or disadvantage. Go here for reasons why either may apply.
² See Variant: Skills with Different Abilities.
³ Only add if the Dexterity check involves the Acrobatics, Sleight of Hand, or Stealth skill and you are proficient in the skill.
*Contest. Sometimes an individual's efforts are directly opposed to another’s. The outcome is determined by a special form of ability check called a contest. (77) A Dexterity (Stealth) check is often opposed by a Wisdom (Perception) check. Go here for more details.
Working Together. Sometimes two or more characters team up to attempt a task. See Working Together.