Make sure you can push down on the board with the weight of your body. I need to use a small stool to do this at our house.
1. Push both hands into the dough.
2. Pull up the sides with your palms and turn
bread a quarter of the way around.
3. Add flour if necessary to prevent sticking.
4. Repeat until dough resists your pushing, does
not stick to your hands, and is of a uniform texture.
5. Knead a little more.
You can't over-knead a loaf (by hand). You can easily under-knead it.