Okay, just a quick primer on the game mechanics.
As I said before, Serenity uses dice steps. They start a D2, then go to a D4, then D6, then D8, then D10, then D10+D2, then D12+D4, and so on. Sometimes you will get a step bonus (or penalty). That will increase the die you roll by that much. A bonus of one would increase a D6 to a D8 (and a penalty would decrease it to a D4). A two step bonus would increase the D6 to a D10 (and a two step penalty would drop it to a D2). A D12 with a step bonus of one would increase it to D12+D2. And so on.
Most actions will roll an Attribute die and skill die, and add the results together. An example, someone with an Agility of D8, and Guns of D6, were to shoot at someone, they would roll D8, and a D6, and add the results together. The number you are trying to beat is the difficulty number, and starts at 3 (Easy), and goes up by 4. Average (7), Hard (11), Formidable (15), Heroic (19), Incredible (23), Ridiculous (27), and Impossible (31). If you beat the difficulty by 7 or more, you get an Extra Success (for example, causing someone even more hurt on an attack roll). Note, if all the die you roll come up 1's, that is a Botch, and can really hurt (don't Botch when using a hand grenade).
Complex Actions. Here, the numbers you need to beat will be higher, but you keep a running total. Each time you roll, a certain amount of time passes, when your rolls have beaten the number needed, you suceed.
Plot Points. These are your way to change the story in so way to your benefit. Everyone will start with 6 Plot Points. You can have at most 12 Points. Anything over 12 gets turned into Advancement Points. They can be used to increase the amount of die you roll. 1 Point spent would let you roll a d2, 2 Points, a D4, 3, a D6, 4, a D8, 5, a D10, 6, a d12, 7, d12+D2, and up to 12 to get a D12+D12. In order to get the extra die, you have to declare the use of Plot Points before you roll. You can spend Plot Points to increase your roll after the die is tossed, but then it is a straight 1 Point to increase the roll by 1, but you can spend as many Points as you can afford.
You can also use Plot Points to decrease the damage you take. Spend a number of Points like you were getting a die roll, say 3 to get a D6, then roll, and deduct that much damage from what you have just taken. As a further example, you were just hit for 2 Wounds and 2 Stun, and you rolled a 3, you would not take the Wounds, and only take a Stun. If you rolled a 4, you wouldn't take any damage, and a 5 or 6, no damage, but the rest is lost. It only effects the damage you have just taken.
You can also use Plot Points to affect the story. The greater the impact, the more it costs.
Some Assets may require the use of Plot Points. Mechanical Empathy, for example, will cost points, the number depending on just how bad the problem is. Some of the Major versions of Assets would give a bonus of 2 to any points spent. If you spent 3 Plot Points, and had Major Allure, it would be as you had spent 5.
Another use for Plot Points is to improve your character, buy up Skills, get new ones, increase Attributes, maybe buy off a Complication. As said, any after 12 become Advancement Points, to be used to improve your character. Also, if you have more than 6 Plot Points after a session (adventure), the extra become Advancement Points.
Life Points. This is how much damage you can take. When you have taken a number of Wounds equal to your Life Points, better hope the will is up to date. If you take Stun equal to your Life Points, you are out cold.
One final point. In combat, if you hit someone, the more you exceede the number you needed, the more damage you do, before you see what damage your weapon does.
Will go into more detail about combat later, but hope this gives some idea of how the game works. Any questions, feel free to ask.