The past couple of years we've held an informational session with PNMs. The response has been so-so.
We invite the girls and their parents. We all wear polo shirts embroidered with the NPC crest and had APH nametags made up. We are sure to not wear anything that indicates oru affiliation and will request that other alumnae guest do the same.
(In fact, one year an FSU chapter general advisor attended with her niece and was decked out in her chapter affiliation's jewelry , including her chapter nametag. She got very offended when we asked her to remove it all. She pointed out that *we* had nametags and I pointed out that the tags were all the same and didn't mention affiliation. 
)
This year we are planning doing a booklet mailing to PNMs. We are able to request a mailing list from the local public school system and a couple, though not all, the private schools in the area will also provide us a mailing list. We will probably limit the mailing to those young women with a GPA of 2.5 and above.
If you want to look at the presentation we use during our live sessions, it's on our APH site. Link in my siggy.