Now, to elaborate a bit further and detail the approach for delving in the lore of Middle-earth I deem most useful, I generally proceed through these steps in descending order (most relevant and important first). IIRC, a similar one has already been posted by someone else in another thread, so you may find some of that familiarTolwen wrote:Independent of the actual question it's a good example of how we can approach such topics (i.e. deducting given textual evidence and cross-references with real-worl models). Consistency with the text is an important criterion, but IMO far from being sufficient alone. As the cases where Tolkien actually says "XYZ is that way" (and thus no discussion about it) are in the clear minority, we have to use the evidence that is there and comparative models (see above) to deduct from. And this is all about likelihood, i.e. what is the most probable and likely interpretation given all the parameters that we have.
Accordingly, a most likely interpretation may change if new evidence is made available (or unearthed from texts not considered before. Thus the competing interpretations on a given subject must be be measured according to their likelihood within the given context.
Roughly that's the way knowledge is generated in science and it accepts that there is (mostly) no absolute truth and the "truth" may change if the base upon which it is built changes. In the context of Middle-earth, some interpretations of questions based on the Silmarillion alone (i.e. before other books edited by Christopher became available) were "true", while becoming "false" with the successive availability of the History of Middle-earth (or Unfinished Tales) series.

- What has been written by Tolkien on the subject? This is then further sub-categorized.
- The Lord of the Rings and writings contemporary to that or written after in accordance (even if published only posthumously) with its content bear the highest canonicity.
- Then comes The Hobbit (published by Tolkien in his lifetime, but not intended originally for Middle-earth and thus not always fitting well in there).
- Third come the other posthumously published works. Here the relevance has to be measured against the compatibility with the design and intent of Arda as outlined in the LotR (thus the Lost Tales generally have a low relevance compared to later writings on the same subject). The relevance of the given quote must always be checked (e.g. when it was written and which development stage it is and whether this is compatible with the developmental stage of the LotR).
- What do we have as fitting real-world models/ideas? This can and should draw from contemporary (or nearby) eras that Tolkien used himself (e.g. the Anglo-Saxon model for the Rohirrim offers a tie-in for other cultures in the imagined world) or alluded to in commentaries (e.g. his Letters). It also includes real-world writings like the Beowulf, Kalevala or Völuspa or fiction like the House of the Wolfings which inspired Tolkien as well.
- What has been written on the subject by RPG authors in their supplements and what are your own ideas? Existing RPG supplements (of whatever game line) will be compared and measured against the results of the first two points and either be accepted as fitting (perhaps with modifications - big or small) or rejected as not having a sufficiently solid base. Similarly, your own ideas are subjected to the same standard and with the same principles.
- Write your final conclusions on the subject once the process from the previous points has been finished. Ideally, this will result in something imaginative that both adds further detail to the imaginary world and in the same instant is based as far as possible on the original source and methodology.
Cheers
Tolwen