Ice first, then vodka
Fill a highball glass with large, dry ice. Add vodka and chill it briefly, then pour freshly opened tonic slowly over the ice. This reduces foaming and loss of carbonation.
Adjust tonic to taste
Use less tonic for a spirit-forward serve and more for a longer, lighter drink. Too much tonic can become thin and excessively bitter as the ice melts.
Choosing a garnish
Lime is a clean, classic choice. Express a little peel over the glass and taste before dropping in the wedge, as too much citrus oil can cover a delicate tonic.