Depending on what the subject matter is and how complicated a painting might be, I create a fairly detailed drawing on regular drawing paper in pencil. This practice is especially important if I'm doing a commissioned house portrait or other complex composition. Once I'm happy with the sketch (or the customer is happy with it, if it's a commissioned piece), then it's time to transfer the drawing to my stretched watercolor paper (see blog from April 2023 on how I stretch my watercolor paper).
I turn over the drawing and coat the entire back of it with graphite, using a soft black pencil. Then I turn over the drawing, place it on the watercolor paper, and tape one side down so it doesn't slide around while I retrace all the lines and transfer all those details onto the watercolor paper. I don't press down too hard, just a gentle pressure; I don't want to emboss the lines into the paper, just lightly coat it with the graphite, so that I have guidelines to follow when I get to painting.
Once the tracing process is complete, I lift the drawing paper off the watercolor paper. Then I tape around all four edges of the transferred drawing on the watercolor paper with white artists tape, so that I can have a clean edge around the painting.
It may seem like a tedious and archaic process, but it's what has always worked for me. And I enjoy all the steps. I have saved every drawing I've done for each painting...probably should organize those into some sort of archive some day.