I love a good martini. I prefer gin...vodka is one spirit I don't care for much at all... and find I like a 5 to 1 ratio of gin to vermouth. Prepared just as Rick described. Awesome.
Andrew, fool around with the ratios and see what you prefer. Some like 3 to 1, some 5 to 1, some 1 to 0, it's all personal preference. I like mine with olives, but too much olive flavor takes away from the martini for me.
The good thing with gin, relative to some of the brown spirits we both like
, is it is a relatively affordable spirit. Even some of the best (my favorite is Hendricks) can be had for less than $40 (even less than $30 on line). Vodka? I have no idea. Cheers!