Select the correct tungsten electrode geometry and size. A sharply pointed tungsten electrode will result in a wide, shallow weld, while a blunt tungsten electrode is conducive to a deeper weld. Using the correct tungsten size is also critical to welding precision. An electrode 1/8 inch in diameter, for instance, will not weld base metal that is 1/16 inch thick with a high degree of precision.
Select your filler metal, which should be lower in thickness than your base metal, so the filler metal does not need excessive heat to melt. The filler metal, as well, should have mechanical and corrosion properties similar to those of the base metal.
Set your welder to your desired amperage, which should provide slightly more power than you need. Use the welder to heat your scrap metal. Practice using the fingertip and foot adjustments to increase and decrease the rate at which the puddle forms, by increasing or decreasing the amperage. The weld puddle should rapidly reach the thickness of the base metal; if it reaches a greater thickness, turn down the heat.
Determine how much filler metal you must add to make the weld puddle solidify. Practice turning down the amperage current, and adding filler metal until the puddle solidifies.
Practice pulsing the welding current to help you develop a pulsing rhythm. Pulsing, which involves transitioning between a high peak amperage and a low background amperage, allows your base metal to cool, while still providing penetration from the peak current, thus preventing warping and embrittlement. Pulsing also allows porosity or gas trapped in the weld to escape and provides control over the narrowness or thickness of the weld bead. Start with a pulsing current of .5 or 1 pulses per second (PPS), as practice, and work up. Determine how much pulsing, if any, is necessary to obtain optimal results.