How can I stop those who are non friends sending me PM"s

Damned if i know. I've been getting some weird stuff from women lately.

Click your messages envelope, look for the filter messages button, it'll give you a menu, check the last box, and save.

Tell them you don't care if they're a Nigerian prince or not, you don't want them to send you money.

That would be great! You can set your privacy so that a certain group ( M, F, T, C) can't contact you directly.... it will just show you have a message, and if you aren't interested...you can delete it