Set the welding tool to the amperage recommended by the electrode manufacturer. Since you are welding thin metal, you will need to use an amperage on the lower end of the recommended scale.
Test your welding tool on a small part of the thin metal to determine the appropriate arc length. An arc that is too long -- resulting from an electrode held too far from the metal surface -- will overheat the metal and result in loud, crackling noises. An arc too short, on the other hand, will result in the electrode getting covered in molten metal. Find the right balance before you weld the rest of the thin metal.
Strike the arc against the metal surface you are welding, and open up an arc of the appropriate length. Hold the electrode perpendicular to the surface, and weave it from side to side. Weaving covers a wide area of metal while avoiding penetrating too deeply into the thin surface. The diameter of your weave should be less than or equal to 2.5 times the diameter of your electrode.
End the arc by quickly twisting the electrode away from the metal surface, then pulling it away.