From the West Point Inn to begin the Old Railroad Grade trail. If you follow this trail to the left it will take you up to the parking lot just below the peak and from there it's a short hike to either the Middle or East Peak of Mount Tamalpais.
Going right on the Old Railroad Grade trail it is all downhill. Since this was made for a gravity train, with no engine, it can't really climb and it can't get too steep either. The trail does have some shady sections, but much of it is pretty sunny.
There are a few alternate trails along here that will take you back to Mountain Home Inn, but the railroad grade is much easier on the knees. Once at the Mountain Home Inn you can use the public restroom across the street.