There is actually a separate site for what you're looking for:
http://www.bpdfamily.com/message_board/This site is for people (with or without BPD) to work on themselves and their issues.
I will say one thing... you won't find a guide on what not to say or how not to trigger. There are 256 permutations of BPD and we're all triggered by different things. The message board I referred you to can help you if you give them details about the issues you are having with the person you know with BPD.
Good luck!