The following link is for the Transports Publics Genevois (TPG) which gives information about buses, trams and shuttle boats to get you around the city and the rest of the canton. The TPG network is also known as UNIRESO.
If you are staying in a hotel, a campsite or a youth hostel during your time in Geneva, you are entitled to a free Geneva public transport ticket for the length of your stay here. The tickets are available from your accommodation's reception. Make the most of this great offer!
You are also entitled to a free transport ticket when you arrive at Geneva Airport. The ticket machine is located just before the customs area as you leave the baggage reclaim hall. Make sure you remember to get yourself one - it will get you right into the centre of town for free!