Depending on the type / quality of your soil, I would first dig a trench, at least several feet deep and then add rock salt, before you back fill. The rock salt will help with making a good conduction for your ground. Then lay in your ground rod, which should be at least six feet in length if not longer. They make two kinds of ground rods and that is something else to be aware of. They make galvanized and copper clad. The copper clad is more conductive and has fewer issues then the galvanized rods. As for the gauge of copper wire, I only recommend 8 gauge because 12 gauge is to light of a conductor for grounding purposes. If you can’t afford it, then go with 12 but I highly recommend the 8 gauge. Make sure all your connections are tight and you should be good to go. This is the way to do it right.