If I have an infected cut on my leg, what is the best way to cure it?

Natural Approach. An alternative to daily soap and water which can be drying or irritating to some wounds and expensive topical or oral antibiotics is to use honey. It has antibacterial properties rivaling some of today's antibiotics and has been used for centuries to heal wounds.
Good care. Depending on the severity of the wound you might need oral and topical antibiotics for this see your physician. If not so severe then wash the wound gently two to three times daily with soap and water to remove debris and keep the tissue pink. Apply topical antibiotics; including colloidal silver and keep it covered until healed.
Clean, Culture, Trea. Honey is an excellent method of wound debridement, but it is not an antibiotic...Per se. If the wound is infected, then a topical antibiotic (i.e. Bactroban) and/or systemic antibiotic ought to be employed. This also implies that the wound has been thoroughly debrided and culture of the wound has been done.
Debridement/abx. If you think it is infected i.E red, draining, with pus, fever etc, smart thing would be to see your doc. Treatment, of course depending on exactly what kind of wound it is, would entail adequately removing infected or revitalized material( debriding), antibiotics, and a moist dressing of some kind. If it is a very minor cut, you may be able to get by with some neosporin.