Be sure your drain pan is positioned beneath the oil filter housing. As you remove the oil filter, a bit of oil will drain from both the filter and the point where it seats against the housing.

Unscrew the oil filter and allow the oil to drain adequately before proceeding.

If your oil filter is stuck, you may need an oil filter strap wrench to remove it. They can be found at most auto parts stores. In a bind, you can also hammer a flathead screwdriver through the body of the filter to gain leverage (this process is messy).