Although St. Petersburg is spread out over 650 square km (250 square mi), most of its historic sites are concentrated in the downtown section and are best explored on foot. These sites are often not well served by the extensive public transportation system, so be prepared to do a lot of walking. Bilingual city maps with bus routes marked on them are sold at the bookstore Dom Knigi (62 Nevsky prospect), while St. Petersburg In Your Pocket prints valuable info about marshrutki routes in every issue.
When traveling by bus, tram, or trolley, you must purchase a ticket from the conductor. At this writing, a ticket valid for one ride costs 10R, regardless of the distance you intend to travel; if you change buses, you must pay another fare. Buses, trams, and trolleys operate from 5:30 AM to midnight, although service in the late evening hours and on Sunday tends to be unreliable.
Note that all public transportation vehicles tend to be extremely overcrowded during rush hours; people with claustrophobia should avoid them. It's very much the Russian philosophy that there's always room for one more passenger. Make sure you position yourself near the exits well before the point at which you want to disembark, or risk missing your stop. Buses tend to be newer and reasonably comfortable. Trolleys and trams, on the other hand, sometimes give the impression that they're held together with Scotch tape and effort of will, and can be extremely drafty. In winter the windows tend to ice up to the point where it's impossible to see where you are, so ask the conductor to tell you if in doubt.