There are so many different types of systems for operating the rear brake that it would be impossible to address them all, but most are variations on two themes. Theme one is the drum brake, while theme two is the hydraulic disc brake.
Your typical drum brake may have an old-fashioned design, but there's a lot to be said for its simplicity, economy and effectiveness. Nowadays, drum brakes are most commonly used on smaller road and trail motorcycles, but they're also found on some cruisers models.
The drum brake is activated by cable or rod from the foot lever and will usually have an adjuster at the brake end. An important consideration to bear in mind when adjusting a food-activated brake is that, just like the hand lever type, there needs to be a degree of freeplay to ensure the does not bind on.
Drum brakes are affected by heat and this tends to make the brake components expand, so it worth remembering that the freeplay should still be there when the brake is hot – just don't burn your fingers when you check. And as with a hand lever, the activation of the brake pedal should be a natural act – your foot should be able to move on and off the pedal with the least amount of input. You should also have good leverage on the pedal. Most motorcycles have a brake pedal lever adjuster that sets the lever height, but before setting the lever height you should back off the cable or rod adjuster. Then seat yourself on the motorcycle and without looking at the pedal move your foot on and off the brake and feel if you need to lift you foot in order o use the brake.
Using the pedal adjuster, raise or lower the lever to give you the most natural and easiest movement. The next step is to adjust the rod or cable including a small amount of freeplay, and then go for a ride and check that the brake pedal requires a little more fine-tuning because your position on the motorcycle when riding may differ slightly from when you're just sitting on it at a standstill.
A rear disc brake will not have an adjuster in the fashion of a drum brake as the hydraulic system compensates for any pad wear as it occurs. There will be an adjuster to set the pedal height, though. Use the same technique as for a drum brake to position the pedal for your comfort.