Watercolor paper is expensive, so Instead of drawing directly on it when starting a painting, I work out my drawing on newsprint first, and transfer it to the watercolor paper.. That way, I can re-draw and erase as many times as I need. Commercially prepared graphite paper can cost about a dollar per sheet (they come in a box of 20). The cost of making your own is almost negligible. At the most, it’s a few cents per sheet.
To make it yourself, start by taping all the edges of a piece of printer paper with masking tape to reinforce it. Rub a piece of graphite (or the side of a soft graphite pencil) on the paper in multiple directions to make sure it’s fully saturated. Then, rub a tissue or paper towel over it to help even it out. That’s it! This can be used dozens of times.
To transfer your drawing, I suggest using a ballpoint pen. It helps to preserve the fine lines in the drawing, and you can easily see where you have already drawn.