Geneva is small enough to cross on foot in 30 minutes. Most sights in the old town and along the lake are within walking distance of each other. The city's geography — left bank rising above the lake, right bank flat across to the train station — is easy to orient yourself in.
Public transport (TPG) is excellent: trams, trolleybuses and regular buses cover the city and reach into the suburbs and France. Tickets are around CHF 3 for an hour. If you are staying overnight, your hotel will give you a free Geneva Transport Card valid for the duration of your stay — request it at check-in if it is not offered. The card covers all TPG buses, trams and the yellow Mouettes water taxis that cross the lake.
The Mouettes are a fun way to cross between the left bank and the right bank — four small lines run from Pâquis to Eaux-Vives and back, every 10 minutes during the day.
Geneveroule runs a bike-share scheme with bikes free for the first four hours from kiosks at the train station and several other central points.
The airport is 15 minutes from the centre by train — a free transit ticket dispenser in baggage reclaim gives you a one-time pass into town; for the return journey you need a regular ticket or your Geneva Transport Card.
Taxis are expensive — even short trips cost CHF 25 or more. Uber operates in Geneva.