Change one word to another, one letter at a time. Each intermediate word must be a real English word without apostrophes. Best if you can only use common words that there will be no argument about, but I suppose the ultimate test of allowed words is that they must appear in the official SCRABBLE dictionary.
When someone posts a solution, they can set the next challenge. Please try not to set challenges that are impossible or too hard as that will stall the thread! Three or four letter words are normally the easiest but other lengths can be used, providing they're not too hard!
It's also fun (and a way of unsticking the the thread when it gets stuck) to post a shorter solution to puzzle that's already been solved further up the thread.
Here's WORD -> GAME in fifteen:
WORD WOOD FOOD FOOT BOOT BOAT MOAT MEAT PEAT PEAS PETS PATS HATS HATE GATE GAME
Someone can start by changing WORD -> GAME in fewer than fifteen steps or if you want something even easier try CAT -> DOG.
I was going to mention that although all the words along the route should be in the Scrabble dictionary, the starting point and destination need not be when setting geographical challenges. It turns out that for Paris to Dover that we don't need the new rule as paris is type of herb and the verb, dover, is an alternative to doze!