Originally Posted by Blitersety
A coffee filter and isopropyl alcohol. Dab a little bit of the isopropyl alcohol onto the filter and gently rub off the thermal grease. It should come off relatively easily. Do your best not to touch the cpu or hsf with your hands; the oil could inhibit effective heat transfer.
Wear rubber gloves when you're working with the CPU and heatsink and you won't have to worry as much about getting fingerprint oil on anything.
x2 on the Isopropyl alcohol, but I usually use a paper towel instead of a coffee filter.