This guide is the basic info that I use for playing Disgaea. I tend to play in big picture and normally have access to 4 guides and seeing if making my own will keep it on that list.

This is quick dirty and simple. If people ask for my I might expand but this is pretty much what you need to know if you are looking for a specific unlockable human class, and about item specialists.

Class name: levels and class types needed to unlock

Star Skull: Red/Green/Blue Skull at Level 5
Star Mage: Red/Green/Blue Mage at Level 5
Archer: 3 Mastery in Bows
Rogue: Level 5 Brawler & Warrior
Scout: Level 5 Brawler & Warrior
Ninja: Level 10 Male Brawler & Warrior
Ronin: Level 10 Female Brawler & Warrior
Knight: Level 10 Female Warrior & Mage
Recruit: 30 Mastery in Guns
Angel: Level 100 Female Cleric, Knight, Archer
Majin: Level 200 Male Brawler, Warrior, Scout, Rogue, Ninja

Items have a rarity number that that dictates how many levels they have in the item world, more levels means the higher item level is possible, means better possible growth.

Common (Rarity 33-255) - 30 floors
Rare (Rarity 8-32) - 60 floors
Legendary (Rarity 0-7) - 100 floors

Specialists can be seen on the weapon's secondary tab. To get them freed you must go into an item and kill, or "Subdue", the specialist before progressing to the next level of the other enemies get them. If you miss them they will re-appear in the next 10 levels of the item if it has anymore levels.

Freeing them doubles their effect, and allows you to move specialists between items and combine all like specialists. Warning here you can combine a freed and wild specialists you can make a more powerful specialist that is wild, so watch the item levels before you do this. I have had this done to me before and lost a lot of progress.

The notes that show the "max" are actually the max number for effect, some go twice are high but that is the specialist level that you won't get any more effect for the effort.

Dietician - Increases HP (max of 19998)
Master - Increases SP (max of 19998)
Gladiator - Increases ATK (max of 19998)
Sentry - Increases DEF (max of 19998)
Teacher - Increases INT (max of 19998)
Coach - Increases SPD (max of 19998)
Marksman - Increases HIT (max of 19998)
Physician - Increases RES (max of 19998)

Statistician - Increases EXP (max 300)
Broker - Increases HL (max 300)
Manager - Increases mana (max 300)
Artisan - Increases item potential (max 300, not sure if it is in this version)
Armsmaster - Increases weapon mastery (max 1900)

Alchemist - Adds poison effect (max 100)
Hypnotist - Adds sleep effect (max 100)
Witch Doctor - Adds paralyze effect (max 100)
Amnesiac - Adds forget effect (max 100)
Gangster - Adds deprave effect (max 100)
Professional - Adds critical effect (max 100)

Pharmacist - Resistance to poison (max 100)
Coffee Maker - Resistance to sleep (max 100)
Medicine Man - Resistance to paralyze (max 100)
Social Worker- Resistance to deprave ( max 100)
Firefighter - Resistance to fire (max 140)
Aeronaut - Resistance to wind (max 140)
Cryophile - Resistance to ice (max 140)
Psychologist - Resistance to forget (max 100)

Poison - character looses hp every turn
Sleep - character looses actions for a set number of turns based off of specialist strength
Paralyze - character can not move
Deprave - character can not gain EXP
Forget - charcter can not use special abilities