Just a small bit of trivia..
Ok, I learned at least this much as the week-long school for elders:
Pages 308 and 308 of the All Scripture Is Inspired of God and Beneficial book has a chart of the sources used for translation of both the Hebrew and Greek scriptures. The baseline for Hebrew was the Biblia Hebraica (BHK) and Biblia Hebraica Stuttgartensia (BHS). The baseline for Greek was the Wescott and Hort Greek Text. There were a number of other manuscripts used, as well. Someone else said it earlier: a lot of copying and pasting.
Interestingly, you can find agreement with the NWT in almost every case with some source or some translation elsewhere. If you happen to have, or are able to borrow the reference version of the NWT, take a look at appendix 1D. There is a lengthy listing of other sources that agree with their use of "Jehovah" in the Greek scriptures. The "J" references refer to those sources, which you can find on pages 9 and 10 in the introduction. All of the references have "corroboration" with external sources. The only exception is 1 Cor 7:17. The external source is not listed in the English version because the last revision was 1984, the there has been a new source that corroborates the use of "Jehovah" in that scripture, and that comes from:
"THE NEW COVENANT COMMONLY CALLED THE NEW TESTAMENT"
- Peshitta Aramaic Text with a Hebrew Translation
(par The Bible Society, Jerusalem 1986)
Apparently, they haven't exactly stopped defending their translation. When viewing footnotes in other translations (e.g. the NET), one may find that the course of translation used by the NWT in many places is one way the word, phrase or verse in question could be translated. For example, using "undeserved kindness" instead of "grace" or "earth" instead of "land", such as at Ps 37:29 (land is used in the most other translations, but Strong's shows that "earth" is a valid translation, too, but it appears the NWT is using an eisegetical translation with this verse to fit the JW theology.) Comparing multiple translations side by side is very useful. That's why http://bible.cc is one of the more useful sites for researching, IMO.
There are definitely some key areas where liberties were taken toward the Society's bias. John 14:14, for example, is one where the word "me" is not omitted from the vast majority of translations, including Westcott and Hort's (though in brackets), but is omitted from the NWT. Or Acts 10:36 where the word "others" is inserted in the NWT in brackets where other translations do not include this word.
One thing I have never agreed with is the anonymity around the translation committee and every tract, brochure, booklet, book and magazine article published. The reason for that is because it's unscriptural to say it's to give glory only to Jehovah. Why do I say that? Take a look at the letters in the NT written by Paul, James, etc. They state unequivocally who it is that wrote them (or at least dictated them.) Why not put a name on the articles? It's not as if they're taking away glory from God by doing so. It's so strange...