[header] How to heat and apply solder [title] Cut, file, sand or otherwise flatten the joining surfaces as much as possible. [step] However don't overly polish the surfaces as a slightly rough or' keyed' surface usually leads to a stronger bond. It is crucially important in any soldering task to ensure that the pieces to be joined match up closely with the smallest gap possible. 
[title] Wash the pieces clean and if possible' pickle' them. [step] Pickling means immersing the pieces or covering the joint area in an acid cleaning fluid.