I'll point you to two articles: (1) A previous post I've written that talks about interpreting different genres of the Bible (2) "How To Interpret the Bible" by Matt Slick. Please read both carefully and slowly. Here is an excerpt from the latter source:
The Bible is God’s Word. But some of the interpretations derived from it are not. There are many cults and Christian groups that use the Bible, claiming their interpretations are correct. Too often, however, the interpretations not only differ dramatically but are clearly contradictory. This does not mean that the Bible is a confusing document. Rather, the problem lies in those who interpret and the methods they use.
We need, as best as can be had, the guidance of the Holy Spirit in interpreting God’s Word. Because we are sinners, we are incapable of interpreting God’s word perfectly all of the time. The body, mind, will, and emotions are affected by sin and make 100% interpretive accuracy impossible. This does not mean that accurate understanding of God’s Word is impossible. But it does mean that we need to approach His word with care, humility, and reason. Additionally, we need, as best as can be had, the guidance of the Holy Spirit in interpreting God’s Word. After all, the Bible is inspired by God and is addressed to His people. The Holy Spirit helps us to understand what God’s word means and how to apply it.
Summarily, I would tell your friend:
1. There is a proper and an improper way of interpreting any given passage or verse in the Bible.
2. The proper way to interpret any given passage/verse is to read the text carefully; study its historical/cultural context; find out the author's original intention; understand it in accordance with its genre of writing, ask the right questions about it (such as the ones listed in the "How To Interpret the Bible" or this article) and apply its timeless principle. Remember, you can always make something say whatever you want it to say if you don't do good, solid interpretation.
I'd recommend you and your friend read a good book about proper biblical interpretation such as this free e-book by Gordon Fee and Doug Stuart.
[Answered by Pastor HM]