This is the trick to quoting scripture.  Buy yourself a little mead notebook and copy the verses you want to remember. Use a yellow highlighter to highlight the words.  Whenever you are sitting there, doing nothing look at the verses you have written down and say them over and over again [out loud].  Choose to commit them to memory. This means do whatever it is that you do to memorize things.  Before you know it, you are quoting scripture.  YOU HAVE TO WRITE THEM DOWN!

Deuteronomy 17:18 And it shall be, when he sitteth upon the throne of his kingdom, that he shall write him a copy of this law in a book out of that which is before the priests the Levites:

De 17:19 And it shall be with him, and he shall read therein all the days of his life: that he may learn to fear the Lord his God, to keep all the words of this law and these statutes, to do them:

De 17:20 That his heart be not lifted up above his brethren, and that he turn not aside from the commandment, to the right hand, or to the left: to the end that he may prolong his days in his kingdom, he, and his children, in the midst of Israel.