Look for clear edges in your picture. With this example, you can clearly see the outline of the jug against the background. Notice where the shape crosses the gridline - this is the reference-point that you can use. Don't try to measure where it is on the grid, but rather judge its position (halfway up? one-third?) and find the same spot on your drawing grid. Follow the shape, looking for where the line next meets the grid.
The area shaded gray shows a NEGATIVE SPACE formed between the object and the grid. Observing these shapes can help you follow the shape of the line. Notice how the gray space looks fairly triangular, with a couple of chunks taken out - that makes it easy to copy.