There are ten primary attributes: five physical (strength, constitution, endurance, agility, and hand-eye coordination) and five mental (intelligence, wisdom, willpower, intuition, and charisma). These attributes are used as a basis for most of what your character does. Proficiency in the skills your character possesses will be determined in part by their scores in these attributes.
At first glance, the line between some of these attributes (Constitution and Endurance, Agility and Hand-eye Coordination, Intelligence and Wisdom) may seem fairly fine, but with a little thought, the distinction should become apparent.
In addition to these primary attributes, there are a few secondary attributes. They include hit points, armour class, the various movement attributes, and the optional luck attribute.
For each attribute, its common abbreviation is given, along with a brief description and an example of when it might be used. Also, whenever other numbers are based on an attribute, that is noted.
Whenever a character needs to do something which requires brute force (such as break in a door, or lift something heavy), a check will be made against strength.
If a character should be poisoned, lose a lot of blood, or get sick, checks may need to be made against constitution to determine whether the character lives or dies.
Hit points are determined directly from constitution (see the introduction to Race Descriptions).
If a character ever needs to remain awake for long periods of time, or do some normal physical activity for much longer than it is usually performed, check will be made against endurance to find out whether they can continue.
Checks would be made against agility to find out if a character retains their balance on precarious footing.
If a character needs to make repairs to an electronic component by doing spot welding, their hand-eye coordination had better be good.
Note: This name is somewhat misleading; characters which belong to races without hands may still have a hand-eye coordination. Cats and dogs can certainly manipulate objects with their paws, although not nearly as well as we can. If the race description lists an average HEC, then it is considered to apply to whatever appendage happens to be most hand-like.
If a character is asked a skill-testing question to win a million dollars, the odds of getting it right will be determined by their intelligence.
If a character is asked a riddle to win a million dollars, the odds of getting it right will be determined by their wisdom.
If a character's endurance gives out while swimming the English Channel, their willpower will help to determine how much further they can go on.
If a character is being followed at night, and senses that something is wrong, that's intuition talking. New mothers have instincts about how to care for their children; this is also intuition (for the purposes of this game).
Note: You will not usually use your character's intuition. The GM will generally roll an intuition check on your behalf when there is something that your character has a chance of noticing. By the very nature of intuition, you will not know when it might come into play, but the GM will.
Whenever your character meets someone new, you may wish to use their charisma to try to make the strangers more friendly than they would otherwise be.
Players can give their character luck points when they are created (see Initial Attributes), but this is the last time they will ever know how much luck the character has. Instead, to model the fickle hand of fate, the GM is the only one who knows how muck luck a character has.
The GM may hand out extra luck points to new characters based on such things as original concepts or well-crafted histories. During play, players may earn extra luck points for their characters with good ideas or original solutions to problems, doing an exceptional job of being "in character", paying for the pizza, or whatever the GM feels is appropriate. They may also cause their characters to lose luck points by flagrantly ignoring character vs. player knowledge limits, arguing with other players, getting a soda for themselves but not offering one to the GM, and so on. There is no right or wrong thing to award or deduct luck points for. It is completely at the whim of the GM, and players should never be told.
A player can try to use a luck point at any time. A luck point will allow any toss of the dice directly involving that character to be rerolled (you cannot use your luck on behalf of another character). Luck points used in advance can also increase the chance of success on a given die roll (usually by 10% per point spent, e.g. from 20 to 30, although this number too is at the discretion of the GM). By using enough luck, almost anything can be achieved, but remember that once a luck point is used, it is gone forever.