Oily Skin

Shiny patches

Large open pores

Coarse skin texture

Sallow skin caused by sebum holding dead cells on surface

Blocked pores leading to comedones (blackheads)

Good skin tone caused be grease protecting skin from dryness

High moisture content
Oily skin is caused by an over secretion of sebum, so anything that over stimulates the sebaceous glands (oil glands) should be avoided. For instance:

Excessive cleansing or handling the skin

Overheating

Poor diet
Oily skin easily collects debris and in severe cases lead to cysts and pustules that are found in cases of acne vulgaris.