Bartending, even at home, requires lots of supplies, mixers, and garnishes. In addition to beer, wine, liquors, and liqueurs, a decent home bar should have the following supplies if you plan on serving cocktails. You need one bottle of the following mixers for every five guests:

Cola or diet cola Lime juice
Cranberry juice Orange juice
Ginger ale Pineapple juice
Grapefruit juice Seltzer water or club soda
Lemon juice or lemon mix Tomato juice
Lemon-Lime soda Tonic water

You also need these fruits, garnishes, and seasonings:

Lemon twists Angostura bitters
Lime and lemon wedges Salt and pepper
Maraschino cherries Superfine sugar
Olives Tabasco sauce
Orange slices Worcestershire sauce