The requirements for each of the shouts is being able to cast/manifest level 1 spells/powers.

Great Shout Level 1-
When you get angry a welling of magical energies bursts forth in the guise of a great shout, causing a magical wave of concussive/sonic force to burst in a 30' sphere originating with the shouter.
You are considered to get angry when you are first hit in a combat encounter, and in other scenarios at the DMs discretion. When the potential shouter becomes angry there is a 25% chance that a shout will emanate.
Deals 1 point of damage to objects within 30'. Hardness is reduced by two. The Great Shouts only affects objects that normally shatter, such as glass, wood, clay, etc.
Deals 1d4 points of concussive damage to all creatures within 30'. Fort Save (DC 15) or be stunned for 1d4 rounds.

Great Shout Level 2-
The same as level 1 but with the following changes: Deals 2 points of damage to objects, damage is upgraded to 1d6 within 40' and the save DC is raised to 17. The chance of an accidental shouting when becoming angry decreases to 15%. The shouter is now able to initiate a shout herself once per day.

Great Shout Level 3-
The same as level 1 but with the following changes: Deals 3 points of damage to objects, damage is upgraded to 1d6+1 within 50' and the save DC is raised to 20. The chance of an accidental shouting when becoming angry decreases to 5%. The shouter is now able to initiate a shout herself twice per day.

Mind Shout-
Unlike the Great Shout the Mind shout can be used at the shouters discression. The Mind shout can be used two times a day, and has two uses.
A shouter can gather a welling of magical/mental energies and focus them at the mind of a creature with an intelligence of 2 or higher. The target must make a will save DC 10 + spell caster level or be stunned for 1d4+1 rounds.
The second ability of the Mind Shout is to send up a mental 'signal flare' telling all creatures with an intelligence of 2 or higher who you are and where you are. The range is 1 mile per two spellcaster levels.