Sevcik Cello Studies are a superb collection of exercises to help develop bowing style, accuracy, rhythms and wrist speed/strength. Part 1 of Op.2 of this excellent series covers: How to hold the bow, Movements of the bow, Dividing the bow-length, Staccato and Legato, Detached and hopping styles of bowing, Dynamic changes, spiccato and arpeggios.