Something that will give your skin the hydration it needs without adding to its oil issues, ie something light or gel based. Some to try: DDF's Daily Matte moisturiser (£36 at Harvey Nicks); Clinique's Dramatically Different Moisturising Gel) or Simple's Oil Control Shine Management moisturiser (£3.79). And you don't have to put this all over - just put it on the bits that need it. Also, be gentle when you cleanse your face - if you use a strong wash-off product to 'tackle' the oily bits, it can backfire, by drying them out and making them scramble to produce more oil to compensate, while drying out the dry bits still further - a wash off-cream cleanser or a cleansing oil is kinder.