A trip round the lake is lovely.You can stop off at Evian and Montreux I think or alternatively a trip through the Haute Savoir to Annecy is wonderful.The scenery is breathtaking and Annecy is a delightful town to visit
easiest way geneva to annecy is by car, if you don't have a car there's a bus service leaving geneva (gare routiere) at 8h30, 10h30, 13h30, 17h30 & 18h45, and from annecy ay 6h30, 8h15, 10h15, 14h15 & 17h15; journey time 75mn.
the train takes 2hr15mn & involves 2 changes at annemasse and la roche sur foron.
Train for 30 mins or so to Nyon along the lake,then right outside Nyon station electric tram up into the mountains about 45 mins picturesque village of San Cerge,or similar spelling, look around roman town of Nyon on return to Geneva. Very easy and enjoyable trip in less than a day.