Offer a pre wed, or a trash the dress sesion. I haven't heard much about trash the dress, but I saw some photos of a cousin of mine she took at some cenotes (pond in a cave) near Cancun Mexico and they were awesome. A wed dress shot underwater was a great shot.
Offering discounts at expos might work in the short term. I think it depends on how full or empty your shooting agenda is. The problem is when there are so many expos that everybody start's to wait for one to get a discount, and then really, everybody's working with a 20% discount all the time
In Mexico where I am, there is an wedding expo every 3 months, so for couples that plan ahead, they might wait for one to select a photographer instead of requesting the services before hand.
Also, find the locations (restaurants, gardens, haciendas, etc.) where some or most weddings are hosted and give them your contact information. Contact groups that sing at weddings, wedding planners. Offer them some shoots of the band, organization that they can use to help them keep your name in their minds.