Turn on your soldering iron. If your soldering iron has temperature control:

Set it to 300 °C (~570 °F) if you're using leaded solder

Set it to 375 °C (~700 °F) if you're using lead-free solder

Clean the tip of your soldering iron. If you're using a sponge, wet the sponge and quickly wipe the tip across it. If you're using brass wire, stab the tip into the wire a few times.