While the iron is cold, if the tip still has its original silver looking coating, just wipe it clean with steel wool. Then let it heat up to soldering temperature and touch a piece of solder to it, then wipe quickly on a wet sponge, leaving a solder coating. You will find that having a wet spone handy to ocasionally wipe the iron will keep it clean. After the silver looking coating wears off with use, then you have to file the end of the tip so you get the copper look all over. Try to maintaint the same shape. Once you get the shinny copper, plug the iron in and hit the tip with solder again as above, wiping the excess of on the wet sponge. Don't keep the iron on any longer than necessary as the tip will oxidize rather quickly. I just rigged up a simple timer (like you would find on an appliance) that will shut the iron off after 15 minutes or something less that I have turned the timer to. It is also hand to have some paste flux to coat the iron with before and after wiping on the sponge. Spemding a few minutes with someone skilled in soldering would be worthwhile. Seeing it done makes it quite simple. I've probably given as many soldering lessons at the Clinic as I have battery lectures.