“Do to others as you would have them do to you” is the greatest piece of advice about how to love others.  It is truly a golden rule.  Every faith, every great religious belief, has a version of it for people to follow:

Judaism says it this way:  what is hateful to you, do not do to others.

The Hindu faith says it this way:  do naught to others which would cause you pain if done to you.

Confucianism tells us:  do not to others what you would not have them do to you.

Islam says:  no one is a believer until you desire for another that which you desire for yourself.

These are the great rules of love, the great rule by which you can tell if you are loving others even when you do not feel loving towards them.  Can this rule be fulfilled in your life?