Materials list:
a sketchpad (around 9x12 - something comfortable to carry)
variety of your favorite drawing tools: pencil, three or more ballpoint pens (multiple colors- Pilot, and InkJoy work great), colored pencils, charcoal, markers, etc.
One piece of medium weight watercolor or printmaking paper 9x12 or larger (my favorite is Rives BFK)
Gesso (an 8oz bottle is enough)
a 1"-2" sponge brush or gesso brush