You've got to go where the herps are, when they're out.
If you want frogs, go out at night or after rain so you can find them by their calls. Different frogs call in different seasons and from different habitats, so check wooded and field ponds, riverbanks, swamps, and temporary wetlands, any time from mid winter to late summer. Gray treefrogs should be calling right now, from almost any pond, lake, swamp, sluggish stream, or even water-filled gutter or ditch. A flashlight and patience will let you find calling males.
Terrestrial salamanders are easiest to find when it's relatively mild. If its too cold, too hot, or too dry they retreat underground. If it's very wet they often go out foraging, which increases the chances of a random encounter but decreases the chances of finding them under stones and logs. Rocky wooded slopes, bluffs, and areas near streams and springs are often best.
Streamside salamanders are less affected by the weather. Look for streams too small or intermittent to have populations of large predatory fish. Springs are often productive. The best cover objects to turn are moderate-sized objects that cross the dry land/water boundary.
The pond-breeding Ambystoma species usually come to the ponds in late fall and winter, during rains. Drive along roads at night and you can often see large numbers crossing to their breeding pond. Minnow traps left out overnight can also catch large numbers; just be sure to set the traps late and collect them early to prevent salamander deaths. Winter-breeding frogs, overwintering tadpoles, and newts can also be caught at this time.
