Why not start with Leonardo?
Leonardo da Vinci used his sketchbook to record things he saw in nature, to work out ideas for new inventions and to see form and gesture more sensitively. His sketchbooks can still be an inspiration to us today.
click on thumbnail for larger view. 

Sketchbooks for Drawing

additional sketchbook samples

Ideate

Sketchbooks for Painting

ideate and make notes about other artists.

Sketchbook 
for Figure

Use sketchbook to practice skills, proportions, perspective, body parts and how other artists draw the human body.
Click on thumbnails for larger view. 
Student Gestures for Figure

Sketchbooks for Design

ideate

Journals