Chill your martini glass or coupe in the freezer for 5–10 minutes.
Fill a mixing glass with large ice cubes, then pour in 2.5 ounces of dry gin and 0.5 ounce of dry vermouth.
Using a long bar spoon, stir the mixture with the ice for 30–45 seconds until well chilled.
Remove the chilled glass from the freezer and strain the martini into it using a cocktail strainer.
Garnish with either a lemon twist (twist peel over the drink to express oils) or skewer 1–3 green olives on a cocktail pick and drop into the glass.