It is hard to improve on these answers! Trust, respect, communication, surprises, back rubs and foot rubs, having someone to tell you that they will always be there for you and mean it, weekend get aways, little love notes left in briefcases, lunches, on the mirror, texting each other with pet phrases for each other. I also like the fact of taking a class or hobby together-something that your mate may have expressed an interest in a month ago or maybe even a decade ago. Telling each other "I like you" is big too. You can love someone but if you loke them and they are your best friend, it changes things around.