As a pastor, I have been asked this question many times. Not a few, but many. And it is a question with many possible answers. So let me explain how I approach this question. It may help, and it may not.
There are two basic ways people translate the Bible. One is to translate the Greek into English, word for word. Translations which follow this are ones like the King James Version (KJV), New King James Version (NKJV), English Standard Version (ESV) and New American Standard Version (NAS). These texts take the words found in the Greek, and while rearranging them a little for coherency, don't change any of the words themselves.
The other way to translate the Bible is called Dynamic Equivalency. This is remarkably different, and is found in translations like the New International Version (NIV), the New Living Translation (NLT) and the Holman Christian Standard Bible (HCSB). Instead of word for word, these are thought for thought. Assuming that many of the words don't mean the same to us today as they would have in the days they were written, translators feel comfortable not only rearranging the words, but in using ones which aren't in the original text in order to make the ideas which the author was talking about get across.
So which is right? To be honest, I don't know. I'm not a professional when it comes to the original languages. But even if you were to ask the professionals, they would give you two different answers. That is why those who are eminently familiar with the original languages have done it these two different ways.
Understand that there are bad translations, but all the ones I have pointed out have merit, and critics, and are all fairly reliable.
Actually, if someone asks me which translation I think they should read, I usually follow up with a question of my own. Which translation are you the most familiar with? Once they have answered that question, I like to point them in the opposite direction. For instance, if you have spent most of your Christian life reading the NIV, which is true with me, I suggest you go read one of the word for word translations. Take a look at the ESV, for instance. If you grew up with the NKJV, maybe it's time to look at the NLT.
I also think it can help if you are studying a passage to have both types of translations with you. Find a parallel Bible which has both types of Scripture so you are getting all out of the passage you can.
The reason is because these two different texts can be so different that it can provide you with fresh insight on a text you've read many times before. Take a look at John 1:14, first in the NLT, and then in the ESV.
"So the Word became human and made his home among us. He was full of unfailing love and faithfulness. And we have seen his glory, the glory of the Father’s one and only Son."
"And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth."
While the text is not remarkably different, it will cause you to read, study and understand the passage differently. Or perhaps it will give you some new way of approaching an old truth. Either way, this, I believe, can be valuable.