Don't worry about eating oysters when there's no 'R' in the name of the month. They're edible all year round (but in summer they're more palatable cooked than raw).
You can tell if an oyster is fresh because its shell is firmly closed or if open will snap shut when tapped. If it stays open, make sure there is a clean, sea-sweet smell and clear liquid before eating.
A 'drunken' oyster is much easier to open than a sober one. Carbon dioxide does the trick; after 5 minutes in carbonated water, its muscles relax and the shell is easy to open.
If you don't have a knife, put the oysters on hot rocks close to the fire - they'll open up immediately. Or wrap them in wet seaweed and lay them on hot coals for a minute or two.
Cook opened oysters quickly over a low heat so that they don't become tough. The best way is to poach them gently in hot milk or sauce, just until the edges curl.
If you're grilling oysters in their shells, steady them by sitting them in rock salt or propping them up with crumpled aluminium foil.
