SocIsCool

Hi there! I have received several messages about Penn wait list. I received the "official letter" from the graduate chair( very interested in admitting but waiting for the authorization of extended offers) invitation to the campus visit followed by several emails about the campus visit. Penn is my top choice so if there is anyone admitted chooses not to go, plz inform them as soon as possible~I do appreciate it! 
 
Any more question, free to PM me!

I kindly suggest again to the folks here to not being too obsessed about ranking, talk about your interests. I see so many folks here talking about "aha! top 10", "well, top 20/25". It is meaningless unless you have no idea about your research interests. When you are about to graduate, TT positions/job talks will perhaps look at (in order of priority) #1 your publication #2 who is your adviser, #3 your recommendation letter, and maybe well then your program. 
I received two top-10 offers this year but declined them right away to choose Brown. With my interests in family, social demography, urban soc, China and life course/aging, No place will beat Brown, despite its ranking is a 25. Look, I am not even talking about money.

I'm not sure which program in particular @redhillgirl is talking about, but many sociology PhD programs don't interview (some do, but by no means all). I do think that informal conversations are pretty common -- I've spoken with a number of POIs but always after I emailed them to express interest in their research and to ask if they'd want to hear more about my own interests.

Yeah, I didn't mean to make you nervous, sorry. I don't think any professor would expect you to be an expert on their work, but being somewhat aware of their research interests might help start a conversation. This isn't their first time at the rodeo, and they probably expect applicants to not have much substantial expertise, but to have research interests and a little bit of experience. 
My interview experiences were slightly different than SocIsCool -- after a couple brief questions about my research interests and experiences, the profs tended to want to talk about their own upcoming work (since many researchers are extremely focused on their upcoming projects) and how I could fit into it. With two in particular, it felt like what they wanted to know about me was what skills I had, or what interests I had that could translate to them assigning me to a particular project. 
So bottom line, the interviews sound like they vary quite widely from professor to professor. I personally think the fact that this person is giving you an informal interview is a great sign that he or she might be looking to take on a new student. But no pressure!

One tip if you, like me, are an over-preparer who scours CVs (possibly not relevant to the OP): if the profs you're talking with haven't published in a research area for a number of years, there's a chance they moved away from that interest and aren't looking for someone to work on a project like that. And if in their papers on a particular topic they are only second or lower authors, chances are that that subject is someone else's passion, and they were roped in as either senior scholars, or to do number crunching or something like that. I made that mistake with one professor, telling him my favorite paper was one he had published about five years ago as second author, and he was like, "oh ok well that was actually my student's paper, really, and I just helped with the [number crunching, essentially]"… Maybe all this is obvious to many people, but I wasn't really familiar with how author order and that sort of stuff worked when I was an applicant.
Anyhow, I don't know if all this would apply to critical theorists and such, so YMMV...

I wouldn't send him anything he hasn't asked for. If you Skype with him and he suggests that you send him some of your materials, then it would be appropriate. My guess is that he'll ask about your interests, history, experience, etc. Usually these conversations (at least in my experience) are almost entirely about you and not so much about the POIs themselves. They want to get a feel for how you might fit into the department and how the two of you, in particular, might work together. Chances are he's also not going to grill you on his work. Try not to be too nervous -- just speak from what you know!

I'm not sure which program in particular @redhillgirl is talking about, but many sociology PhD programs don't interview (some do, but by no means all). I do think that informal conversations are pretty common -- I've spoken with a number of POIs but always after I emailed them to express interest in their research and to ask if they'd want to hear more about my own interests.

Congrats! That's a great sign.
I found the Skype interviews I did unnecessarily nerve-wracking. From my experience, they were trying to ascertain whether my research interests would be a good fit with their own, and what skills I could bring as their RA. I was so unfocused that I was trying to adapt my research interests to whoever I was talking with -- in hindsight, that was not an ideal gambit since it can lead to a program where you're not actually a good fit. But it is a good idea to try to really research their recent work (though it sounds like you already have). One other thought -- a very smart friend of mine with a very impressive CV and GREs only got into a very low-tier program because her research interests were TOO focused, and most of the programs were like, uh we don't have anyone doing EXACTLY that tiny area. Like, she told me that only three scholars were working on this area, and one was at Berkeley, one at Harvard. So that was not a great strategy…  

If I had it to do all over again, I would recommend 1) sincerity, 2) somewhat focused but not overly narrow research interests, 3) making sure that you're truly compatible with specific faculty at the programs you are applying to. 
It sounds like you have already anticipated all these recs, but maybe it could be helpful for others reading...

I agree with @Pennywise and would add that no matter how casual/informal the conversation may seem, treat all discussions with POIs as if they are formal interviews. Any correspondence (chats, emails, and so on) with a POI may be reported or forwarded to an admissions committee. But I think if you're sincere (like Pennywise said), if you're simply yourself, and if you don't let your nerves get to you too much, you'll be just fine.

Honestly, that would be a bad idea. You've presumably spent 1-2 years working on the masters thesis. And yet, if it isn't presentable enough as a writing sample (in abridged form or full), then that may be considered pretty damnning.
By the way, what was your undergrad GPA?

Actually, I have spoken to a sociology PhD student who was enrolled this Fall and she told me she had a point or 2 lower than me in both sections, a 3.8 GPA and no research experience and was still accepted. Her writing sample and other areas must have been good but she told me she knows for a fact that her GRE scores was not the reason she was accepted. 

This may be off topic but I feel like Sociology PhD programs that look for high scores in everything, ironically end up perpetuating inequality. You know for damn sure that the MAJORITY of students who have nearly a perfect package with high GRE, high GPA, lots of professional experience, top 40 college, etc. do NOT come from a socio-economically disadvantaged background.  There may be a few but as sociologists, we all know that the majority of students who have access to resources and opportunities are from privileged backgrounds. How is this even fair? What's the point of teaching and researching about social inequality if they won't practice what they preach. What a load of bull.