Question:
What types of sources/resources do you use when exploring your religion, and how do you establish a criteria within which to evaluate them?
In addition, are any of these resources contested? If so by whom and why?
At the start of my exploration into Kemetic reconstructionism, I learned the interpretations of the major temple groups (at the time: House of Netjer, Akhet Hwt-Hrw, and Per Ankh). Kemetic religion is highly complex, and too vast of a subject for many people to just jump in to the academic texts and start assimilating facts- without some sort of a framework to hang it all on, the information you pick up lacks a meaningful context. For me, the temple classes provided that initial framework.
These days, my understanding of the religion is based largely on what I've learned from academic quality books and original sources- I use those sources, and personal experience illuminated by those sources, to continually re-examine my old framework and occasionally rebuild it. Since I do not claim any sort of past-life knowledge of ancient Egypt, or an unbroken lineage of teachings passed down from the priests' hands, I accept the fact that occasionally the interpretations of ancient Egypt conceived by modern students of the culture may be revealed to be inaccurate and in need of adjustment. This would not cause a crisis of faith for me, as I know my limitations but feel that my intention to be as respectful of tradition as I possibly can is a pleasing gift to the gods and in accordance with ma'at.
To find sources I trust, I prefer books published by academically respected Egyptologists- I read the "about the author" sections to look for degrees, areas of activity, and motivation for writing the book. I pay attention to publishers, and favor books printed by universities or publishers with a reputation for their selection of academic level texts. I try to buy books with as recent a publication date as possible, since new discoveries can change our views at any time, but I'll make allowances for an earlier publication if the author has credentials and his or her information seems to be reasonably in line with what I've read in other books. I cross check, preferring information which is verified in several books which have met the standards I laid out above. I usually avoid books written by non-reconstructionist Pagans, or anyone claiming a past life as a platform of authority for their writing on the subject. I'll read them for inspiration sometimes, especially if they're well written, but it's been my unfortunate experience that non-recon Pagans often do not have the same value for research and sourcing as recons do. After all, they're coming at the religion from a different perspective. As for past-lifers, I have trouble remembering specifics from my own childhood in
this life, so recollections from past lives just don't impress me with great confidence for accuracy- even assuming that the past life experiences are 100% legitimate. The veracity of a past life experience is something I can't verify one way or the other anyway, and a subject on which I prefer not to pass any personal judgement, but memories fade and can be faulty. I want information which is supported by what we're actually finding in the field.
The best way- in my opinion- to figure out which books are trustworthy and which aren't is to read a lot of them. After a while you get a feel for the different schools of thought within the field, and the methodology of each Egyptologist. Then you can use the bibliographies of the ones who impress you to find the works which that Egyptologist trusted enough to use as a basis for his or her own work, and you get a feel for when to take the theories of other authors with a grain of natron.

If someone proposes an idea which flies in the face of the ancient Egyptian culture as currently understood, that's a red flag. That doesn't mean it's automatically to be rejected, but it requires further study to determine whether the author's conclusions are justified. However, that sort of judgement call requires a well rounded familiarity with ancient Egyptian society which can only come from having read and become familiar with many studies on many subjects.
That's why this is such a tricky issue for new Kemetics- in order to judge which books are good learning material you really have to know what sorts of things they ought to be teaching. It's a catch 22 for those who are trying to enter the study, which is why most temples provide reading lists to get people started. Those very books from the temple lists might prompt a student to question that temple's interpretation of the faith, but I think that's good. Nobody here has all the answers, and it's best that people keep asking questions so we don't forget that fact!