But to get back to the process of lassoing.

As our cowboy gets close to his quarry, he takes the noose in his lasso hand.

I will use my left, as it is a trifle handier for me.

He grips the rope, not too firmly, holding the standing part and the side of the noose about half the length of the loop away from the knot.

That is to enable him to swing the noose so that it will fall open.