As you're soldering, regularly wiping off the hot iron tip with a brass or damp cellulose sponge is your first line of defense in keeping the tip functional.

Brass sponge: Small brass coils that have a similar texture to steel wool, but more wiry. Also called "brass wool," "brass tip cleaner," or "brass cleaning ball." Many solderers prefer it because it's long-lasting, low maintenance, and doesn't drop tip temperature.

Cellulose sponge: Usually come with most soldering workstations. Not as long-lasting as a brass sponge and must be kept damp (not soaking wet!) with distilled water while in use.

Synthetic sponges can melt and damage your iron tip. If you're using a sponge, be sure it's made out of cellulose.

P.S: Most kitchen sponges are synthetic!