The Martini is one of our favourites because tiny changes make a completely different drink. Every Martini drinker has a preference, and they tend to be very particular.
Start with the spirit. Vodka or gin? It depends how adventurous you're feeling: gin brings a lot more flavour, vodka gets straight to the point. Grab your favourite bottle, or try something new. A Martini is a great way to taste a spirit.
Now the vermouth, which is what we mean by dryness. For bone dry, rinse the chilling glass with vermouth and tip it out. For dry, use 5ml. For wet, 15ml. Dryness matters almost as much as the spirit.
Like it dirty? Add 10 to 15ml of olive brine. If someone orders it dirtier than dirty (filthy, or any other unclean adjective), go up to 30ml. Dirty Martinis always get three olives.
Then the big question: shaken or stirred? Bond likes his shaken; we usually stir. If you do shake, fine-strain out every shard of ice. Finally the garnish: olives for dirty, a lemon twist for everything else.