The dough should be a little bit sticky. It should stick to the bottom of your mixing bowl as the dough hook does its kneading, but not the sides. If your dough is sticking to the sides of the bowl, however, it is too sticky. This can happen sometimes in the summer, when it is extra humid in the kitchen. Add a little more flour 1 tablespoon at a time until the dough pulls away from the sides of the bowl. But don't add too much, or you'll end up with dense bread.