Someone will put one letter and then the next person puts another letter. You can add a letter if you know of anything that has the letters that are already listed.
Example:
#1 puts P
#2 puts Po
#3 puts Por
Your can continue with any letter that will end up making a ride, resort etc at WDW or whatever the game is. In the above example the starting letter could be for Port Orleans, Pirates of the Caribbean, Portobello Restaurant or even Peter Pan's Flight.
So it is random and what the first poster thought of could be totally different from what it ends up being.