The following are house rules for Luck Points and Force Points in my Star Wars RPG campaign.
Minimum Force Point Bonus of 2
Any die rolled to determine the benefit of the expenditure of a Force Point will yield a minimum of 2. (In other words, treat any roll of "1" as if it came up "2".) The reason for this is simply to make the expenditure of a Force Point slightly less anticlimactic when the dice aren't cooperative.
The following house rule is instituted for the sole purpose of giving adventures more of the "feel" that my playing group is accustomed to, using certain other gaming systems. (Well, that and helping the PCs stay alive longer.)
Skill Checks, Ability Checks and Saves
The basic use of a Luck Point is to spend it to alter the outcome of a die roll, either for his hero, another hero in the party, or any non-player character present. Spending a Luck Point will add 1d6 to any check or save that has just been made. Multiple Luck Points may be expended to further enhance the effect, but the total benefit gained cannot exceed +6. (Any "extra" points are wasted.)
Luck Points may also be spent to increase weapon damage, but the total damage, regardless of Luck Points spent, cannot exceed the maximum that could have normally been rolled for that weapon. (For example, no matter how much Luck is involved, a Stormtrooper blaster rifle -- which normally does 3d8 damage -- will never do more than 24 (3x8) points of damage.)
Luck Points may be spent to absorb damage. Each Luck Point spent will negate 1d6 of the damage dealt from a single attack. (No damage can do less than zero points, of course.)
Accumulating and Spending Luck Points
Heroes may accumulate Luck Points during the course of play, at the whim of the Gamemaster, represented by poker chips used as tokens to keep track of how many have been gained. A player spends a Luck Point by tossing a token back to the Gamemaster. At the end of the session, any remaining Luck Points are recorded on a blank spot on the character sheet.
Intervention on Another's Behalf
Luck Points may be spent by any player to benefit his or her own hero, another hero, or even a non-player character. However, there must be some conceivable way, no matter how strained, that the player's hero is somehow intervening on the behalf of the recipient. For example, it may be that the hero is shouting, "Look out!" at just the right moment, or offering words of encouragement, uttering a fervent prayer, et cetera. A player's hero cannot intervene in situations he is unaware of and/or unconnected to, though the player can always spent Luck Points on behalf of his or her own hero. (i.e., even if a hero is stunned, a Luck Point can be spent to absorb damage taken by the hero.)
No Obligation to Intervene
Please note that under no circumstances is a player obliged to spend a Luck Point on behalf of another character. Refusing to spend a Luck Point does not in any way mean that the hero is guilty of withholding help from another character in need. (The reason for this distinction is so that cautious players are not obliged to repeatedly "bail out" suicidal heroes who have already blown through their cache of Luck Points.)
Limitations of Use
The Gamemaster reserves the right at any time to declare that Luck Points may not be spent on a particular roll. For example, if a hero were to run into a room full of Stormtroopers with a live thermal detonator and let it explode in his hand, confident that he has enough Vitality Points and Luck Points to survive the incident, the Gamemaster may declare that no matter how much Luck he has, he is going to feel pain. (In fact, a stunt like that may even deserve bypassing Vitality and going straight to Wounds.)
Excess Luck Points
At the end of each game session, any Luck Points kept in excess of the character's current experience level are lost. (During play, however, there is no limit to how many Luck Points may be acquired.) If the Gamemaster awards any Luck Points at the finale of any game session, then those points are exempt from this limitation (as there's really no chance to spend them at that point).
Awarding Luck Points
Luck Points may be awarded by the Gamemaster at any time during play, as a reward for coming up with clever ideas, defeating difficult opponents, solving a puzzle, performing some admirable act, or coming up with an in-character humorous quip, for example. Or, for a particularly tough session, the Gamemaster may simply give each player a Luck Point at the start of the game with a warning that they'll probably need it before the session is over.