All metal must be clean for solder to flow. Clean the metal by sanding it with 400-grit sandpaper. Surfaces must be in complete contact with each other for solder to flow — solder will not fill holes or gaps. Apply flux to all metal to be soldered to prevent oxidation and to help solder flow. Heat the entire piece, not just the solder. Keep the torch moving in a circular motion.
If there is more than one solder join in a piece, solder the first one using hard solder, the second using medium solder, and the third using easy solder, as hard solder has the highest melting point and easy solder has the lowest. To keep the solder in a previous join or joins from flowing when you heat the metal again, apply an anti-flux to those areas.
During soldering, the solder will flow to where the heat is the greatest. If your solder is flowing in the wrong direction, adjust the direction of your flame.
Once the solder flows, quench the piece in water, and place it in a pickle solution to remove oxidation and flux residue. Rinse the piece in clean water.