Hey you might remember the Druid from my last question well while him and I were talking we got on the topic of prestige classes.He said wanted something like a witch doctor.We looked in our core books and couldn't find anything like it. So we searched for other books that might have a class like this.Again no answer.So I told him I could just create a class like this for him.Are there any rules or guidelines for this. Or do I just wing it all the way.Thanks in advanced
To begin, I have written an enormous discussion of homebrew class design for 3.5. It focuses a considerable amount of attention on prestige classes. I stand by every word in it for Pathfinder as well as 3.5. I consider that answer, more than this one, to be the answer you want to read.
But I do want to address Pathfinder specifically:
For Pathfinder specifically, you have to consider whether or not you would like to continue Paizo’s trend of downplaying prestige classes. Personally, I feel like they were overcompensating for any issues 3.5 had in this regard, and made prestige classes too small a part of the game. Your mileage may vary; lots of people love the fact that almost no one in Pathfinder uses prestige classes.
If you do go that route, I recommend doing so by making small prestige classes – three- and five-level deals that you can hop into for a neat, unusual trick, without taking too much away from your base class. I made similar recommendations for 3.5, but in that case it was mostly because I wanted to countermand the tendency in 3.5 to favor ten-level prestige classes even when it wasn’t warranted; ten-level prestige classes certainly can be a good idea in 3.5, you just need to make a class that deserves it.
In Pathfinder, that’s still true, but by the precedent set by other Pathfinder material, you shouldn’t make ten-level prestige classes. Yes, I know Paizo has: I would consider that a mistake in light of their desire to down-play prestige classes. Instead, they just made the prestige classes simply not that great, or too painful to take because of how a diversion from your base class affected you. I consider that less than ideal. Instead, just make smaller prestige classes.
Small prestige classes don’t have to be small in concept; in fact, being small gives you freedom to be really specific and detailed. It means less work per prestige class, and fewer demands on characters’ levels, which means they are more likely to be able to afford those levels for some niche thing.
On the other hand, you can reject that Pathfinder paradigm, and return to 3.5-esque prestige classes, where they are significant and important, and it is often less a matter of if you will prestige class, but when and in which. If you decide to go that route, my 3.5 advice fits perfectly.
There's no "Class Construction Guide" or anything like it.
It's not something you can really do by adding features worth X points each, as there will always be certain combinations that create overpowered/underpowered choices. That's why they're designed "by eye" and then tweaked over a period of playtesting.
Generally, you rely on playtesting to achieve a sense of balance, too. While theoretical balance can give you useful data, generally you want a large sampling of playtesters to see how it feels to each of them, and then adjust accordingly.
For a home game, just wing it. Compare what you've come up with to other prestige classes. If possible, try and find something that can be reflavored and tweaked a bit. If you find yourself asking the question "have I made this too powerful?" then you probably have - err on the side of caution, as it'll be easier to tweak it upwards during play than to take away something you've given your player later.
There are no prestige class creation rules for Pathfinder.
Keep in mind that Paizo stuff tends to have more archetypes for full classes; prestige classes are reserved for actual prestige orgs in the game - like joining the Red Mantis Assassins or the like. Something you want to just always be - like your witch doctor example - is usually instead represented as a class archetype or even a new base class. I understand there will be guidelines for creating them yourself in the upcoming Advanced Class Guide.
If you do create a prestige class, here's a good set of questions to ask yourself (stolen from a Paizo forum post here):