Matthew 22:34-40 — But when the Pharisees had heard that he had put the Sadducees to silence, they were gathered together. Then one of them, which was a lawyer, asked him a question, tempting him, and saying, Master, which is the great commandment in the law? Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets.

So how are you doing on that? Observing the greatest commandment, and the second? I have to say that I am not really doing as well as I would like to.
The first thing, I suppose, is to know what the two commandments are saying. Mathew has Jesus giving them as I quote them above, although Mark and Luke tells the story slightly differently, inserting “strength” between “soul” and “mind”.
In the first commandment “heart” is heart as in the sense of whole-hearted or half-hearted. It is not about emotions, but about commitment. We are to be fully committed to loving God. It is the soul that is the seat of the emotions. Loving God is not just an intellectual or moral choice — it requires passion, all the passion I can command. Strength is not, I think, mere physical strength — it is the strength to endure. Finally, whilst loving God is not an intellectual choice, it does require the exercise of the intellect. We cannot love what we cannot understand. 
The second commandment seems simpler — love your neighbour as thyself. The complexity, of course, is tied up in the definition of who my neighbor is (which is the lawyer’s follow-up question). Jesus tells the parable of the Good Samaritan to make the point that anyone can be a neighbor — and that the relationship should be defined by need, nothing else.
There’s another “little” issue to consider, though … Why does Jesus say the second commandment is “like unto” the first? The obvious link is in the phrase “Thou shalt love”. But how is loving my neighbor like loving God? One key is that my neighbor is made in God’s image — from that point of view, loving my neighbor is certainly like loving God.
As I said at the start, I don’t really do as well as I would like. I can be distracted from loving God as I ought — and I find it really hard to love some of my neighbors! I’ll keep trying though …