When travelling from Geneva Airport or Geneva down town to other Swiss venues, in most of the cases, public transport is the best solution, and notably the great Swiss Rail system. All the schedules and prices are available on http://www.sbb.ch/en/. And this includes buses, boats and sometime even cable cars (when they liaise two places). Tickets can also be bought on-line.
From the airport, input "Geneva-Airport" as departure station. It is located right to the left when exiting the airport's main terminal. Tickets can be bought either at one of the machines (card & cash payments are possible) at the station or at the ticket booth (when attended).