First, pick your poison. A classic Dry Martini is gin, because gin tastes like a Christmas tree had a baby with a juniper bush. If you use vodka, you’re making a Kangaroo (yes, that’s the real name), and that’s totally fine—just don’t call it a Martini in front of a purist.
I’m going to assume you’re using gin, because we’re fancy today. Really good gin. The cheap stuff will make you sad, and sadness doesn’t pair well with olives.