So quickly we forget the sandwich board signs and sound cars used in yesteryear.
Also, the WTS takes advantage of articles in local newspapers advertising and explaining the conventions. The internet is peppered with such news items.
Then there are handbill campaigns
*** yb07 p. 7 Highlights of the Past Year ***Another example of praise given to Jehovah was the three-week global campaign to distribute the special handbill advertising the "Deliverance at Hand!" District Conventions, held in some 155 lands. Millions of Kingdom publishers in over 99,000 congregations shared in the campaign, the first of its kind.