A martini should not be straight gin, or anything close. The martini is the perfect blend of gin and vermouth, with just a touch of orange and lemon.
Fill a shaker or glass with ice, then add the gin, then the vermouth, then the bitters. Stir (do not shake!), then strain into a cocktail glass. Take a twist of lemon and twist it until a drop of oil drops into the liquor, then drop the twist into the liquor. Absolute heaven.
Do not use olives or onions; nor should one use less than a 1:6 ratio of vermouth to gin under any circumstance.