Gently place the steamers in your sink (Or a large bowl). Using your spray nozzle give the clams a good cleaning on the outside by spraying them with cold water.
Fill the sink with cold water, enough to just cover them. Add to the water 1/4 cup of cider vinegar, gently swish the water around. The vinegar helps the steamers to expel any sand or mud in their digestive tract. Keep gently swishing the steamers around and allow them to soak for about 15 to 20 minutes.
Drain the water off and take the spray nozzle to them one more time. You will never ever get all the grit or dirt off or out of a steamer clam, but this will get them as clean as possible.
At the Grill
Check your charcoal grill: Make sure you can close the cover all the way with your sauté pan inside. Start your coals and wait for them to get evenly hot.
Now place the steamers in an oven proof sauté pan, with the juice of 1/2 of the lemon, and the white wine, water, olive oil, diced onion, and salt and pepper.
When coals are hot place the sauté pan in the grill uncovered, and then close the lid of the charcoal grill.
Occasionally give the clams a stir, gently, cook for approximately 8 minutes. Keep an eye on them as charcoal grilling times may vary; When all the clams are open they are done.
You'll want a metal-handled sautè pan that will fit entirely on your closed charcoal grill.