Luck

Good Luck

+2 if PC is blessed
+3 if you have the lucky intrinsic (naturally)
+6 if you have the fate smiles intrinsic (naturally)
+1d12+1 if it's your PC's birthday
+2 for every equipped item that grants luck (equipped correctly)
+4 for every equipped item that grants fate smiles (equipped correctly)
+3 if you're wearing the Anhk or Platinum Girdle (they do not stack, so having both is still +3)
If (1d100 <= Mana) Then add Max(1d(Mana * 0.1+2),4)

Now, add all of that together and roll 1dGoodLuck-1 to get your actual luck roll.

Note that Mana itself sometimes counts towards Luck effects outside of the normal luck roll.

Bad Luck

+2d2 if cursed (naturally)
+3d5 if doomed (naturally)
+1d(number of items that give the cursed intrinsic * 3)-1
+1d(Number of items that give the doomed intrinsic * 8)-1
+1d200 if PC is "out of luck" (triggered from editing save files or such)

Note that being Doomed in itself will also further impact many situations beyond the luck roll penalty above.

In most situations these are used, Good Luck is rolled and then BadLuck is subtracted from that roll, to end up with whatever positive or negative bonus to the situation.