There are, after all, not just the Ten Commandments in the Torah, but as many as 613 commandments... 248 positive ones ("you shall...") and 365 negative commandments ("you shall not...")
So, among all these commandments, how to sort, to prioritize: which is the greatest?
Jesus said in response, "'You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.' This is the greatest and first commandment. And a second is like it: `You shall love your neighbor as yourself.' On these two commandments hang all the law and the prophets."
Love God with all you've got, and love your neighbor as yourself. It's as simple as that.
As Michael Moynahan, S.J. has written in his poem/prayer "Broken Record,"