The best method of avoiding this disease is by being adequately immunised. Also if you are wounded, clean the wound but if you are worried about contracting tetanus, only us light dressing as the bacteria will die upon exposure to the oxygen in the air.
You do not automatically get tetanus just because you stood on a rusty nail for example. It depends on how deep the wound it and whether you have been immunised recently for the disease, also on how clean the wound is.
Always dress wounds properly - this means all cuts, abrasions and punctures. If the object which contributed to your wound came from the ground - dress the wound as best you can and see a doctor immediately. He or she will advise you further and possibly give you an updated tetanus shot if you havent already been immunised in the last 5 years.
Make sure you have your whole family immunised against tetanus and keep records.
When to seek further professional advice