Common American Toads live east of the Rocky Mountains and are found in both the forest and the suburbs. The females are larger and can get to be four inches long or so. Males are typically only seen during the spring migrations for mating. Other than during the spring migration, the best time to look for these toads is on rainy summer nights. Toads come out after dark to feed on slugs, bugs, etc. By the summer time they can be far away from the breeding ponds they used in the springtime - so don't bother looking in the ponds themselves.
A bright headlamp or flashlight is the best way to spot them - their eyes should reflect brightly enough to be seen from 40+ feet away.
A toad is, in general, slow and not prone to sudden movement, unless it is disturbed. If you see the toad first, your chances for some good pictures are better than if you scare the toad accidently while walking. Leave the dog at home - they are just a nuisance if your goal is to find toads.
Once you've disturbed the toad, you have very little time before the toad gets restless and hops away. There's really nothing you can do about it - just let it go on its way at that point.
Since you'll be photographing at night, follow the tips below on nighttime photography.
I have found in general that the larger the frog, the less restless it is. There are several species of frogs in the United States and Canada, but the most common large frogs are the American Bullfrog and the Green Frog. The bullfrogs can reach six inches long or more, and can eat just about anything that can fit in their mouths - bugs, mice, birds, bats, fish, snakes, etc. It's somewhat more rare to find a very large "green frog" than a bullfrog.
Bullfrogs are much harder to approach than toads, but they are easier to find. In nearby parks/wetlands, there can be predictable sightings near the water's edge.
Bullfrogs are more comfortable (less restless) in the water than on land. When you approach one on land, it is likely to hop towards the water.
For land approaches, I prefer nighttime. This makes the frogs easier to find. See the below tips for nighttime photography.
Daytime is the best time to approach via the water in a kayak. Expect the frogs to hop / swim away many times. Unlike toads, once the frog has hopped away once doesn't mean you should give up. Be patient and try again.
Moving slowly is the key. Establish yourself in front of the frog for several minutes before you attempt anything. Don't act like a heron. With practice, you can slowly lift a bullfrog out of the water from underneath with the palm of your hand, but in general, it's best to leave the frog right where it is. Don't put the frog anywhere where it won't be able to get back to the water easily - you don't want the poor frog hopping around in the bottom of your boat.
The eyes of the frogs and toads are very important to the picture. You want a well exposed, closeup picture without a strange reflection in the subject's eye.
What you want is a "diffuser" - a light source that scatters light. You can pay big $$$ for one, or you can make one cheaply. Carry a white slightly translucent bucket with you to hold your equipment. When you find your subject, turn on several of your flashlights / headlamps inside the bucket - congratulations, you have an excellent diffuser. Move it as close to your subject as you can.
Keep the flash off. Use the headlamp on your head to provide additional light as needed. Brace the camera on the ground and take a picture as close as you can, using your "macro" mode. If your camera offers frame stacking, use it.
I personally use a Olympus TG-5 waterproof camera. Since the lens is internal, it has a very short focal length and an excellent macro mode.
Do everything you can to get the toad looking at the camera and to be upright. The toad on the left (Stacy) is looking at the camera but is also looking down somewhat, depressed, lacking caffeine and/or sugar. If you can, prop up the toad on something.
The toad below is upright, which makes him look engaged, studious, perhaps angry but not bored.
The problem with propping up a toad is that it is likely to bother the toad far more than the hats. Be ready to take picures quickly. Time is of the essence.