Here, I'm not good at explaining things so I took photos of how to get the proper grip:


Then, clamp your thumb down onto the leash


Then, take the leash and wrap it over your thumb


Finally, place the rest of your fingers on the leash like so:


That's the grip When the dog is on the other end of the lead, stand with your feet planted shoulder width apart. That stance plus this grip should give you maximum control.