My trick for making the perfect Martini is ice cold gin! Keep your bottle in the freezer along with the mixing glass you'll use to make it. The reason for this is to prevent as much dilution from the ice as possible.
STEP 1. Tale your mixing glass from the freezer and add cubed ice.
STEP 2. Pour 15ml of dry vermouth (my preference is Noilly Prat) into the mixing glass - or pint glass if you don't have one.
STEP 3. With a bar spoon, stir gradually coating the ice.
STEP 4. Discard the vermouth, keeping the ice in the glass (if you don't like your Martini too dry leave the vermouth in).
STEP 5. Add 50ml of gin - I like Tanqueray Ten for a modern twist.
STEP 6. Stir.
STEP 7. Pour into an ice cold Martini glass.
STEP 8. Garnish. Some people like a twist of lemon, others an olive. Some even like both! But for me, I like a twist of grapefruit that picks up on the existing fruit notes in Tanqueray Tenand coats the surface of the drink with fresh grapefruit oil - a nice touch which adds subtle dimesion to the drink.
STEP 9. Serve!
STEP 10. Drink.