How is kidney failure usually treated?

Dialysis or transpla. If you mean complete shutdown of the kidney, then it would mean dialysis either through blood ie hemodialysis or through the stomach called peritoneal dialysis. If the loss of kidney function was gradual, your doctor could send you to get listed for a kidney transplant if your function is less than 20% or you could have a relative or friend donate a kidney.
Treat causes. Depending upon the cause. Most common causes are associated to hypertension and diabetes, medicines (narcotics, non steroidal antiinflamatories, toxic dye or contrast, toxins from bacteria (e.Coli enterotoxin), streptococcal causing nephritis, viruses, vasculitis (lupus) treat the underlying disease, protect the kidneys with good hydration and medicines like aceinhibitors. Dialysis if severe.