Your Dog will lick you when
He is exercising Love and Trust. Sitting on the couch reading the Sunday paper and your pooch suddenly jumps up in your lap and begins to slowly lick you. He is just being a bit emotional and is simply showing you some doggy love. Those slow licks are translated to "Hey, what's up? Are you OK?" Yes, that is your dogs way of just telling you that he recognizes you and he thinks you are his buddy and he trust you.
He is asking for a bit of Emotional Attention. You know when your dog wants to go out or when he is in the mood for some dog romping. He will bark, jump run and be all excited. But when that same dog simply needs a bit of conversation, a little petting, scratching and hugging, he will simple give you a couple of licks mostly in the face. He is simply saying, "hey! put down the remote and give me a scratch or a hug."
He is worried for you. Many times when dog owners become ill, your dog will know as they have a natural instinct to sense illness. Once this happens, your dog will express comfort towards you by licking you. He is simply saying that he is sorry and worried that you are ill and wants you to get better quickly.
You are part of his belonging. Normally when dogs mark there territory they prefer to use urine. Your dog knows that he can't mark you with urine so he does the next best thing. Why not leave some doggy saliva on you. Once he licks you, he acknowledges that you belong to him and he belongs to you. In other words, you have just been owned.
You are his pal. A couple licks now and then is to just reassure you that you are his pal. In other words he thinks of you as a much more intelligent dog.