Regarding transportation, you'll want the new 7CHF 9am-12am day pass, or the 10CHF 24-hour version if you arrive earlier.
Both cover every means of public transportation in and around Geneva: trains, trams, busses, and even the shuttle boat in season.
If taking the train to the central Cornavin station, be warned that the train station does not advertise them, and will sell you a more expensive, train-only ticket.
Buy the pass at the bus stop upstairs; the machine only takes coins, and does not give change back, IIRC.
Taxis are overpriced, with a 10 minute ride costing as much as a pretty good meal (~30CHF).