One of the best ways to see amphibians in the early emergence is to drive slowly down back roads at night looking for frogs and salamanders in the headlights.  It never fails to surprise me the numbers of frogs crossing roads on a rainy spring night.  Frogs will begin to start moving before they really start singing, so you'll see species you wouldn't hear.  Leopard Frogs, Green Frogs, and American Toads are commonly seen on the road during the spring.  (The pictures on this page were taken on asphalt at night.)  It helps if you know places where frogs frequent later in the year and drive by those places while searching.