The NWT translators arbitrarily decided when to use the word "Jehovah" and when to use "Lord". While they sometimes use "Lord" in reference to Jesus, at other times they translate it as "Jehovah" even when the reference to Jesus was clear.
Especially objectionable to those who are not Jehovah's Witnesses is the NWT translation of John 1:1 as "In (the) beginning the Word was, and the Word was with God, and the Word was a god." This follows the Jehovah's Witnesses doctrine as, to them, Christ was a created being. He is to them, not God, but a god.
Theological bias can be seen throughout the New World Translation text. As the Jehovah's Witnesses do not believe in the deity of the Holy Spirit, these words are never capitalized. As they do not believe that Christ died on a cross, their translation makes reference to a torture stake rather than to a cross.
The Witnesses do not refer to the first division of the Bible as the Old Testament or the second as the New Testament, so their translation designates these parts as the Hebrew-Aramaic Scriptures and the Christian Greek Scriptures, making a distinction in language with an implication that the OT is not Christian.
The translators of the New World Translation used a good Greek text as a basis for translation, and did a relatively good job of it except in those areas in which the actual text disagrees with Jehovah's Witness doctrine.
In [the] beginning God created the heavens and the earth. -- Genesis 1:1
Now the earth proved to be formless and waste and there was darkness upon the surface of [the] watery deep; and God’s active force was moving to and fro over the surface of the waters. -- Genesis 1:2