TEXT: HEADS or TALES is a rules-lite roleplaying game 
  system that lets you and your friends tell a 
  fun/wacky/exciting 
  story 
  together 
  with 
  minimal 
  supplies needed. One person is the Game Master (GM) 
  moving the story forward and acting as the world, while 
  everyone else are the Players acting as characters in 
  that world. All you really need is a coin, but it can help to 
  have a couple tokens handy as well (more coins, bottle 
  caps, etc.). Heads or Tales is meant to be played 
  anywhere, so take it with you on the train, to the bar, or 
  anywhere else you want to get your roleplaying fix. 
  Once you all decide on what sort of story you 
  want to tell, start flipping those coins!
  Coin Flip System
  As you tell your story together, whenever 
  you try to accomplish a task that might 
  have a consequence, flip a coin and call 
  it. If you called it correctly you complete 
  your task, nice job! If you get it 
  wrong...look out, the GM is going to throw a 
  complication your way. The GM might ask 
  you to make multiple flips for a 
  complicated task, but remember 
  this game is supposed to be lite 
  and fast, so keep the story going!
  Reaction Examples:
  Example 1: 
  Player: “Ok, I’m going to stab that 
  ugly orc right in his ugly face”
  GM: “Call it!”
  Player: “Heads...get it?”
  GM: “It’s heads! You stab the orc 
  right in the face. The only thing you 
  regret is that pun.”
  Alternative Rule - Tokens
  The core of Heads or Tales is the 
  simplicity of the coin flip that drives 
  the story. But sometimes you like to 
  have a little control over fate. An 
  alternative rule you could include 
  has  everyone, including the GM, 
  starting the game with two tokens 
  in front of them (e.g. bottle caps). 
  Whenever a player wants a 
  reflip, give a token to the GM 
  and flip again. Careful though, 
  the GM can make you reflip 
  with their tokens. When a GM 
  makes you reflip, they have 
  to give you a token. The 
  tokens keep getting traded 
  around as you tell the 
  story!
  A simpler way to use tokens 
  is to have every player, but not 
  the GM, start with three tokens in 
  front of them. Whenever a player 
  reflips, throw away a token, it is gone 
  forever. Use things you can eat or drink to 
  make the tokens really feel gone (candy and 
  shots work great for this).
  Example 2:
  Player: “Ok, I’m going to stab that 
  ugly orc right in his ugly face”
  GM: “Call it!”
  Player: “Heads...get it?”
  GM: “It’s tails! The orc swats your 
  sword out of your hand. What do 
  you do?”
  
  WizBotGames.com
  Asking Questions
  Remember, you aren’t 
  telling your story, you’re 
  telling a story together. 
  Because of that, ask 
  the players questions! 
  “What do you do” is the 
  most important, but also 
  ask your players how their 
  characters feel about the things they 
  are encountering. Learn about the 
  characters and the world with 
  questions. Encourage the players 
  to 
  ask 
  you 
  and 
  each 
  other 
  questions too! That world isn’t going 
  to build itself, and the story has 
  multiple 
  authors. 
  Get 
  everyone’s 
  voice in the conversation.
  As the GM of the session, it is up to you to help move the story along. 
  That doesn’t mean you dictate the story though, let the players 
  contribute as well! Heads or Tales is all about telling a fun story 
  together, so let them help you tell the story. If you need some helping 
  getting your story started, check out one of our supplements to 
  get you up and running with one of many genres.
  The GM oftentimes will describe a scene and then see how the 
  players react to it. The single most important thing you can do 
  is ask the players “What do you do?” Turn the focus back to 
  them, react to their decisions, be a character in their story. 
  Supplements!
  Having trouble coming up with your own starting 
  scenario or need a creative jumpstart? Check out 
  our free Heads or Tales setting supplements that 
  will help you get a game started in a whole host 
  of genres!
  Harm suffered 
   
   
   
  Attract attention or trouble
  Doesn’t work as well as planned  
  Takes longer to accomplish
  The problem isn’t what it iinitially seemed
  Consequences
  As the GM, you are supposed to throw consequences at the 
  players when they don’t call the flip correctly. How dire those 
  consequences is up to you, and the general vibe of the group. 
  Are you looking for gritty realism? Throw some harm their way. 
  Looking for a pulpy adventure? Create inconvenient walls that they 
  need to figure how to get around. Keep in mind that if they don’t call 
  the flip correctly, it’s no fun to just say “It doesn’t happen, sorry.” 
  Here are some consequences to get you thinking:
  
SOURCE: textdata/thevault/Kid Friendly/3. Rules Lite Collection/Heads or Tales/Heads Or Tales - Core Rules.pdf