http://carm.org/religious-movements/jehovahs-witnesses/bad-translations-jehovahs-witness-bible-new-world-translation

Bad Translations of the Jehovah's Witness Bible, the New World Translation (NWT).

1.Gen. 1:1-2 - "In [the] beginning God created the heavens and the earth.
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," (New World Translation, emphasis added). A.The Watchtower Bible and Tract Society denies that the Holy Spirit is alive, the third person of the Trinity. Therefore, they have changed the correct translation of "...the Spirit of God was moving over the surface of the waters," to say "...and God's active force was moving to and fro over the surface of the waters." 

2.Zech. 12:10 - In this verse God is speaking and says, "And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and supplication. They will look on me, the one they have pierced, and they will mourn for him as one mourns for an only child, and grieve bitterly for him as one grieves for a firstborn son" (Zech. 12:10, NASB). A.The Jehovah's Witnesses change the word "me" to "the one" so that it says in their Bible, "...they will look upon the one whom they have pierced..." 
Since the Jehovah's Witnesses deny that Jesus is God in flesh, then Zech. 12:10 would present obvious problems--so they changed it. 

3.John 1:1 - They mistranslate the verse as "a god." Again it is because they deny who Jesus is and must change the Bible to make it agree with their theology. The Jehovah's Witness version is this: "In the beginning was the Word, and the Word was with God, and the Word was a god." 
4.Col. 1:15-17 - The word "other" is inserted 4 times. It is not in the original Greek, nor is it implied. This is a section where Jesus is described as being the creator of all things. Since the Jehovah's Witness organization believes that Jesus is created, they have inserted the word "other" to show that Jesus was before all "other" things, implying that He is created. A.There are two Greek words for "other": heteros, and allos. The first means another of a different kind, and the second means another of the same kind. Neither is used at all in this section of scripture. The Jehovah's Witness have changed the Bible to make it fit their aberrant theology. 

5.Heb. 1:6 - In this verse they translate the Greek word for worship, proskuneo, as "obeisance." Obeisance is a word that means to honor, show respect, even bow down before someone. Since Jesus, to them, is created, then he cannot be worshiped. They have also done this in other verses concerning Jesus, i.e., Matt. 2:2,11; 14:33; 28:9. 
6.Heb. 1:8 - This is a verse where God the Father is calling Jesus God: "But about the Son he says, 'Your throne, O God, will last for ever and ever, and righteousness will be the scepter of your kingdom.'" Since the Jehovah's Witnesses don't agree with that they have changed the Bible, yet again, to agree with their theology. They have translated the verse as "...God is your throne..." The problem with the Jehovah's Witness translation is that this verse is a quote from Psalm 45:6 which, from the Hebrew, can only be translated as "...Your throne, O God, will last for ever and ever; a scepter of justice will be the scepter of your kingdom." To justify their New Testament translation they actually changed the OT verse to agree with their theology, too! 

The NWT translation is not a good translation. It has changed the text to suit its own theological bias in many places.