We are using Ramzour's Six Ability Save System.
Saving Throw = d20 + Ability Mod + Prof Bonus (if proficient in this ability) + Situational Mods
The saving throws are spread across all six abilities.
STR: to resist any effect that forcefully moves, restrains, or paralyzes you.
DEX: to dodge instantaneous attacks (area attacks, beams, projectiles, or rays); to avoid traps; to maintain your balance; to stay on a mount.
CON: to resist effects that target your Health or Body (poison, disease, necrotic, energy drain); to resist cold or thunder effects; to endure ongoing environmental effects; to maintain your Concentration; to endure hunger and thirst; to push the body past its comfort limits (for example, a forced march).
INT: to see through illusions; to avoid being tricked or confused. Intelligence is mental cleverness.
WIS: to resist fear effects; to resist psychic or radiant damage; Wisdom is mental fortitude and conviction.
CHA: to resist charms, enchantments, and compulsions; to stay connected to your Plane. Charisma is your force of personality, sense of self, and centeredness.
Acid, Fire, Lightning: generally a DEX save to indicate dodging the stream or bolt.
Cold: generally a CON save to indicate resisting the effects.
Force: generally cannot be saved against.
Necrotic, Poison: generally a CON save.
Psychic: generally a WIS save.
Radiant: generally a WIS save, indicating the mental fortitude to resist damage that "overloads the spirit with power."
Thunder: generally a CON save, as you can't dodge a thunderclap.
Hold person is an enchantment spell, not a conjuration, so a CHA save applies.
http://community.wizards.com/forum/product-and-general-dd-discussions/threads/4107836?page=1