I like a good Freeform game but it does require more work for both Player and Game Master.
A pure Freeform is the hardest of all. In my opinion it should be played only by people who are friends or long term writing partners.
Simply put the Game masters role in pure free form is sharply reduced. The players have much more control over the narrative then in most games.
Part of that is that it isn't a game. It's an interactive story. Players both IC and OOC make many of the decisions. In many cases the distinction between PC and NPC even disappears as Players divide the task of running minor characters among themselves.
I've played this kind of game twice . We had five players. We began each session with a IM conference where we laid out the basics of the adventure: Who the antagonists were, what kind of obstacles would be encountered, what 'actors' would be included and roughly what their role would be. In some cases even where we wanted the scene to go and invented some twists and turns for the actors to encounter.
Then we played the scene. Like a good story the characters came on stage one by one and were properly introduced. They met each other (or not) and the Problem was presented or occurred. The characters made a plan and thyen set out to execute it. But the Plan failed! The characters were now in a pickle. They had to make up a plan quickly.
That plan of course works and the problem is solved but in many cases another problem is foreshadowed.
But as I said this level of trust and commitment is rare.
So we must then retreat to a system where the GM assumes a more familiar role and tells the story, runs NPC's and in many cases calls the shots.
That works well actually if the GM has the political skills to carry it through. Since the same political skills are present in more rules bound games a Free form game of this sort can work well.
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I Run several games in this category and find certain formats work quite well.
I always ask players for a profiles of their character(s) and then I put it where other players can see it.
I do ask for a backgrounds description and a skills list. This a simple way of preventing a character being an expert in everything.
Sometimes I will ask players to compose a character with game rules but only use this as a reference in resolving skills and confrontation tests.
But the easiest way of limiting choice is to assign numbers. This of courses gives the game the appearance of a rules-Dice game but helps players and Gm in understanding the strengths, Skills and Weaknesses of the characters.
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Some might object (and rightly so) that a freeform game's resolutions are done by players. Again this means that the players must trust each other and have some understanding of the game.
A immature player who always must win can ruin a game quickly forcing either the players ejection or education. The first can be ugly and the second can be time consuming.
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A good Freeform game is the best game=story one can have. It approaches the fun of collaborating on a project without many of the worries and pressures of such a project.