The traditional way was the obviously very labour-intensive door-to-door routine. Can't imagine it had a brilliant succes rate, but the lads and lasses really put in the effort.
Nowadays, they've totally changed their tactics. They just stand outside London Bridge station with a bunch of pamphlets that could conceivably be non-religious ("Imagine a Government with No Corruption") and have an audience of thousands in the space of an hour. Of course, it's higher exposure, but it's lower intensity - how does that impact on results?
Apparently part of being a JW is that you have to go out and spread the message and log your hours to prove you've been doing it. I'd be well narked if I'd spent my life door knocking and now the whippersnappers are you just hanging round stations.