One of the most important steps is washing them. These hoard dirt and a good washing in cold water is essential.
I find, filling a big bowl with water and then scrubbing them, a good way to remove all that grime. Repeat the process until the water runs clear
and the peanuts are very well cleaned.
Now add them to a pressure cooker. Add salt to taste and fill it with enough water to cover the peanuts completely.
Note: There is no advantage per se in adding salt right at the beginning since the salt only penetrates the pods after it softens. The early addition of salt also slows the process of cooking the peanuts. But overall, I find the ease of not opening the pressure cooker in the middle reason enough in adding it beforehand. It does not cause any change in texture or too much delay in cooking to warrantee not doing it.
Make sure you are not filling the pressure cooker to the brim (more like half way full) since it would lead to water seeping out while cooking. So use a good sized pressure cooker if making the same quantity. Pressure cook them for 3-5 whistles,around 10-15 minutes.
If you find, once you release the pressure, them not soft enough, cook for few more minutes until it reaches your desired texture. You can also add more salt if needed before this step.
Cool enough to handle the peanuts and shell them to taste the delicious nuts to your hearts content. Its easy to shell them and hardly takes few seconds.