I agree with corazon, 1 part of each vodka/kahlua and then generally 2 parts milk/half-n-half for beginners. More accustomed drinkers may want less dairy :P.
Also as someone said a black russian is the same minus the dairy, coke never makes a presence as some blasphemer suggested!!!
Additionally, the most traditional (and best) appetizer to go with caviar is a good vodka. I'm talking a quality imported vodka here, you will never suspect your drinking the same drink when you taste a good quality russian vodka compared to a domestic version. Serve it straight, chilled in chilled shot glasses, for people to sip as they dine.