Start by taking a highball glass (you can also use a Collins glass for this purpose), and filling it about a quarter of the way with ice cubes. Do not use crushed ice for this purpose, as that will melt far too quickly, and rob your cocktail of its potency.
Once the highball glass is packed with ice, proceed to pour in 2 oz of vodka – there are no restrictions regarding this, and you can use any brand and flavour, provided that the vodka you use is of good quality. Stir with a stirring rod, until the ice and the vodka are properly mixed, and the glass takes on a cold, slightly frosted appearance.
Next, pour in 2 oz chilled tonic water, squeeze in a bit of lime juice, and stir the drink once again, to blend all the ingredients together. Your vodka tonic cocktail is now ready – serve it on the rocks, with a lime or lemon wedge on the rim of the glass, or floating directly atop the drink.