Permission

To write a PPC spin-off you need to obtain permission on the PPC message board.

How To Get Permission
To get permission, there are a few generally accepted steps that you need to trip over. This list was blatantly stolen from Lee Trynace.

6) Find yourself a badfic and write your mission, as based on your reading of previous killings.
 * 1) Hang out around the board for at least a month. This is to get you acquainted with some of the... quirkier aspects of the PPC.
 * 2) Read at least The Original Series, commonly refered to as the TOS. It is also highly recommended that you read several other spinoffs, a fairly complete list of which may be found here.
 * 3) Check out the rest of the random PPC stuff lying around, mostly found here.  Including the intro, constitution, the PPC wiki, the various handbooks, and loads of other random stuff. All very handy, especially the reference book of Suvian species.
 * 4) During your month or so of orientation, think up an Agent or two (preferably two, unless you're PPC'ing with someone). Usually people's first agent is something of an avatar of themselves.
 * 5) After that month, ask for permission to PPC on the board.  Be sure to submit a sample of your writing with it, and then it is up to one of the active Permission Givers to grant you permission.

Araeph on Permission
But, why permission, you ask? The reason is simple, as can be seen from this excerpt unabashedly nicked from Araeph's entry on The Way Permission Works:

"'This is not because of the Suefic, but because when you are writing about your agents and HQ, you are borrowing the world that was created by Jay and Acacia. We don't want just anyone writing a PPC spin-off because we take pride in the fact that our stories are well-written. (What right do we have to mock people's stories if our own writings are just as bad?) If someone asks for permission to PPC, and that person's post is riddled with bad spelling, grammar, and logic, permission will not be granted.'"

An Addendum: Huinesoron on Permission
"In general, non-mission PPC writing, especially group or cameo appearences, don't require permission."

As hS clearly states, permission is not needed for everything.

Permission Givers
This is a list of those who are permission givers. Mind however, that not all of these people are active.
 * Acacia
 * Araeph
 * BeautyID
 * Bjam
 * Doc Filth
 * Greyladybast
 * Huinesoron
 * Jay
 * Laburnum
 * Leto Haven
 * Miss Cam
 * Neshomeh
 * NenyaQuende
 * Rohirric Monkey
 * Techno-Dann
 * Thalia Weaver
 * Tough Cookie
 * TZA.