Points to remember to cover in your studies:
1. Don't forget to study the bones of the shoulder.
2. Attachment points of the muscles--this should then be self expanatory for the function (action) of each muscle.
3. Innervation of muscles:
Deltoid = axillary
Supraspinatous & Infraspinatous = suprascapular nerve
Teres Minor = axillary
Teres Major = LOWER SUBscapular nerve
Pectoralis Minor = medial pectorial nerve (named because it originates from the medial cord of the brachial plexis)
Pectoralis Major = BOTH medial and lateral pectorial nerves
Subclavius muscle = nerve to subclavius (superior trunk of brachial plexis)
Trapezius = accessory neve (CN XI)
Latissimus Dorsi = thoracodorsal nerve
Levator scapulae = dorsal scapular & Ventral rami of C3 and C4
Rhomboid Major = dorsal scapular
Rhomboid Minor = dorsal scapular
Subscapular = upper and lower supscapular nerveS
Serratus Anterior = Long thorasic (damage = winging of scapula)

4. Blood flow arteries and major veins