What do you look for to make sure that Conch is fresh?
Conch should have a nice light pink color.  If it's gray or browned, steer clear.  Like most seafood, the best indicator is smell.  If it smells salty like a walk near the beach, it's fine.  If it smells like a stagnant wharf or a warm dumpster, steer clear. To clean, run it under cold water.  Cut off any membrane, and drain it before cooking.  Conch is chewy, so don't treat it like scallops or lobster.  It can be tenderized through pounding, cooked in a pressure-cooker, food-processed and stewed, or slow-cooked.  Keep an eye on the texture.  Chewy conch is not ideal.
This is assuming you aren't buying conch in the shell.

If you decide to buy the conch in the shell, you’ll need to extract it. Wash the shell containing the conch under cold running water. Carefully drop 1 to 3 whole shells into 6 quarts of boiling water, adding in a tablespoon of salt. Boil for about 40 minutes. Using a fork or other pronged instrument, pull out the conch meat from the shells and throw away the green matter. You can save the shell for decoration if you like. Rinse the extracted meat under cold water.
Another procedure for cleaning out the shell is to whack the bulging side of the shell with a hammer to break it. Slip a knife into the shell and twist it around until you feel the muscle detach from the shell. Grab the piece of meat sticking out and pull hard, then cut away the stomach and tail.

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