Gaining a Prestige ClassA Prestige Class is a way for you to specialize your character and to have a more exclusive role in your abilities or profession. They offer special abilities that are not otherwise available and because of that, they have very specific requirements. The basic idea of a prestige class is that you cannot begin as a member of one. You are expected to have weathered at least a few adventures.
Requirements to become a member of a prestige class can include the following:
One or more skills Above Starting Value
Total Attack Above Starting Value
Special requirements such as Force Sensitive or group membership
Pay the required Character Points
Base Attributes: The character must have at least the specified value of any attribute listed.
Above Starting Value (ASV): A number of points a character must increase a particular skill above what it is was when the character was created. For instance, if one requirement is "Skills (ASV): Investigation (4)" then the player would have needed to have spent enough character points over the course of his growth increasing his Investigation skill by four pips.
Total Attack Skills: Indicates a required die number for all of your characters attack skills (based on character class type). This would include Archaic Guns, Blaster, Blaster Artillery, Bowcaster, Bows, Brawling Combat, Firearms, Grenade, Lightsaber, Melee Combat, Missle Weapons, Thrown Weapons, and any other possible attack skill. Any pips increased on a skill specialization count towards your ASV when determining eligibility, but only as half a pip. So if you have increased Blaster: Heavy Blaster Pistol by 2 pips, then it would count as 1 pip ASV for both the Total Attack ASV requirement as well as Blaster Skill ASV.
Advancing Your PrCWhen you take up a prestige class, you can only increase your depth in the prestige class by following its rules for growth. Each Prestige Class has a set of skills that belong to it. When you spend Character Points to increase your skills, you may only increase those that are part of the Class Skills or specializations thereof. Every time you increase your class's skills by the Skill Number you may spend the Character Points listed for the next level to gain the associated PrC special ability.
Example: If your Prestige Class has a Skill Number of 6, you must raise any combination of that PrCs available skills by a total of 6 pips (again, specializations only count as half a pip for every pip raised), and upon doing so you may spend the Character Points equal to the level your character is advancing to, gaining the associated class benefit. You may only move one additional level between adventures (unless the GM gives you special permission to advance more than one level).
Can you increase in skills that do not belong to your PrC? Yes, you are still free to pursue skills at your desire. But you may only travel further on your PrC chart if at the time of increasing your skills you do not increase anything other than your PrCs skillset. So if you increase a skill between adventures that is not part of your PrCs skill set, you will have to wait until after your next adventure, only increasing Class Skills before you were allowed to advance.
The exception to this rule are combat skills and force skills. All combat skills are available to you, but pips increased in combat skills not specifically outlined in your Prestige Class skill set DO NOT count towards your Skill Number needed to traverse deeper into your PrC chart.
Can you take more than one PrC? Certainly; as long as you meet the requirements for a PrC, you may take it on as well, but again, you can only traverse deeper into a PrC when you increase the skills that belong to that particular PrC and no others, and by an amount equal to or greater than that PrC's Skill Number. The restrictions that you adhere to for skill growth are rewarded fully the deeper and deeper that you progress down your PrC chart.