By ship
Sightseeing trips by boat run from Loch Lomond Shores near Balloch.
There is also a useful passenger ferry between Inverbeg served by Citylink buses and Rowardennan at the foot of Ben Lomond mountain.
By bike
To enjoy the nature, it is best to go by bike. There's a relatively! well-maintained and -signposted cycleway from Glasgow to Balloch called National Route 7. A good place to join it is Bells Bridge over the Clyde by the SECC Scottish Exhibition and Conference Center. It's a fairly flat 20-25 miles.
By car
If you're driving, mind that the road along the northern part of Loch Lomond is pretty narrow for the traffic it has.
By bus
Buses run along the Loch, but not that frequently see above. You should check the departure-times first, as timetable are not usually available at the stops. The National Park Authority publishes a timetable of all the buses and ferries (http://www.lochlomond-tro...) which may be available as a booklet locally.