The Word of Wisdom refers both to Doctrine and Covenants section 89, and also to its interpretation. The scripture is listed here:
As with many issues in LDS doctrine, some aspects are specified, and others are left open-ended. The official list from mormon.org posted above contains a few items that are explicitly banned--you can't claim to be "living the Word of Wisdom" (and be considered worthy of a temple recommend) if you consume them, even occasionally. However, the scripture contains other guidelines whose interpretation is open to debate within the LDS community. In addition to caffeine (discussed elsewhere), the following is debated:
Yea, flesh also of beasts and of the fowls of the air, I, the Lord,
have ordained for the use of man with thanksgiving; nevertheless they
are to be used sparingly; And it is pleasing unto me that they should
not be used, only in times of winter, or of cold, or famine.
Within the LDS community, someone on a pure meat diet would not be ineligible to receive a temple recommend, but personal opinions vary widely on how this should be interpreted.