Use nodes where the path switches from turning left-to-right or vice versa. And then when turning, place a node at the ‘widest’ point in the turn if you need an additional node. This will yield the fewest number of nodes needed to make the shape. Remember you can add nodes later, or adjust the curves, if you need to refine the shape.
It is good to use minimal nodes to complete your shape, and then go back and edit the curves to get the shape you want. The result will be a nicer object shape and better embroidery. It takes practice, but you’ll find that you can quickly analyze a shape and create it in very few clicks, and then the edits required will be much easier.