Let the FDA, your favorite food manufacturers, your congressman, and your state’s Food and Drug Administration know what you think about genetic engineering.
Buy products that state no genetically-modified seed or organisms on the package. Write other manufacturers an email and let them know why you are no longer buying their products. You can contact manufacturers by looking for their web address printed on product packaging. Some also print 1-800 phone numbers, too. Calling an 800 number is also an effective way to let a manufacturer know you are no longer buying their product.
Get involved in a grassroots campaign in your area if you have the time and inclination. Grassroot movements do work.