Google and Adafruit are my friends as usual. Ladyada posted awhile back a sheet of tips from Hakko on how to take care of your soldering iron tips.
I am guilty of several bad habits mentioned. My old Hakko tip had oxidized rather badly and increasing the temperature on the iron only makes things worse.
Hakko tips are not inexpensive, they can be obtained from Adafruit, Amazon, and others. I don't recommend third party tips as you would not want your nice iron or your work to suffer.
