For the perfect potato salad, you should boil your potatoes for about 15 minutes in salted water or until they are just tender and easily pierced with a fork. Most important is to not overcook the potatoes, as this will yield mushy or mealy salad.
Depending on the type of potato salad you are making and the type of potatoes you are using, your cooking times may vary somewhat. For russet potatoes the time will likely be closer to 10 minutes, while for Yukon Gold potatoes it will be closer to 20. The most important thing you can do to ensure proper cooking is to test the potatoes every few minutes.