How can we show our love for God? To love God means to obey Him. If we do not obey God, we do not love him. Obedience is a witness and a sign of our love.
Jesus' command is to love our neighbour as ourselves. Our love for God must be manifested in our love for people.
How should we love our neighbour? Like we love ourselves. Whatever we want for ourselves, we must also seek for our neighbour.
A Christian should love his neighbour more than himself.