Basic question: what are the ways in which a mundane character can cause coup de grace? Are there any ways that haven't been listed here? Sure, coup de grace is a really low level technique, save for making doubly sure something is dead, and if you use the Torn Asunder book, but I want to know.
the rules for a helpless character A helpless character is paralyzed, held, bound, sleeping, unconscious, or otherwise completely at an opponent’s mercy. A helpless target is treated as having a Dexterity of 0 (–5 modifier). Melee attacks against a helpless target get a +4 bonus (equivalent to attacking a prone target). Ranged attacks gets no special bonus against helpless targets. Rogues can sneak attack helpless targets.
As a full-round action, an enemy can use a melee weapon to deliver a coup de grace to a helpless foe. An enemy can also use a bow or crossbow, provided he is adjacent to the target. The attacker automatically hits and scores a critical hit. (A rogue also gets her sneak attack damage bonus against a helpless foe when delivering a coup de grace.) If the defender survives, he must make a Fortitude save (DC 10 + damage dealt) or die.
Paralyzed: some poisons can paralyze, but if you have enough money at a low enough level to attempt to use these...well, why are you even adventuring at this point?
"held": this is italicized in the book, so I would assume it's referencing a spell. But the spell already says it paralyzes the target, already fulfilling the condition. Is this really what is means, or do grappled opponents become helpless?
bound: How "bound" does this mean? Can you slap manacles on the hands and legs (presumably while grappling) and call it bound? Would having another manacle linking those manacles together count as bound? No real description was given.
unconcious: wait until they are asleep, or poisons, or just beating the daylight out of them. I'm not sure a non spell caster has many options here, except in how they beat them up.