I don't have a ping list, but from what I remember posters saying is that some of them keep them in Word or WordPad, it's just a text file that lists the FReeper names, each separated by a semi-colon (;). Then, when you want to 'ping' the group to your new thread, after you post it, hit the Reply button and copy/paste the ping list into the To: field at the top.
You ping someone by typing their name in the reply. That person will see they have a new message ("New Posts to You") and will be directed to your thread. A ping list is just multiple names.
While I haven't kept ping lists ( aside from the fundraiser ) for years, what I used to do was look through posts with replies sympatico to mine, and save the names in a Notepad file. Even so, be prepared for lots of private emails with "take me off yer G-D ping list!"
I keep one copy of my ping list in my FReep mailbox & another in e-mailbox.
You can do what I do and keep it on your FR home page.
Some people keep their ping list(s) on their about page too, that way you don't have to leave FR to get to it.
add to the other comments to keep in alphabetical order. Early on it is easy but once you get 50 or more you can easily start having duplicates (gets them POd) etc.
I have about 6 ping lists .
Keep one master with all in a word type document with red large letters telling the group & the othres in regular black sep by semicolons.
For other groups I also have seperate files & keep them in that file. It depends on how complex your filing system is. For example for Finest now, I have prolly 20 folders & in each multi folders/files. so I need a system like this.
Not sure this made any sense.. but in general it is best to think ahead with your system & structure.
Oh, did I mention that I have the BIGGEST Ping List on the FR?