Funeral ettiquette

In the last 3 weeks I've lost a grandfather and a close family friend. I'm at the age where most of my friends have had their weddings and/or a child. Now we're at the point where the funerals start. Right now the remaining grandparents (age related illnesses) are going fast, and my parents' generation is going through the round of cancers and early heart attacks.

*Disclosure* As a physician, I've had to attend to the many dying patients. Even when I've been really close to the family, it's a different feeling for 2 reasons. First- caring for the dying is my job, so I've been afforded many opportunities to see this process, while a family only loses Dad or Cousin once. Second, I'm not in the Family/Friends circle- I don't have the memories of the patient being full of fun and life. I remember the patient being full of various fluids that needed to be collected and vital signs. But I digress.

Anyway, now that I am going to more funerals, I have a dilemma- What do I do when I stand in front of the open casket? Is there a protocol? For instance, the first degree relatives get to kiss the body, second degree relatives and close friends may touch the body, all others just linger somberly sounds good. I noticed at my grandfather's funeral, most people got to the casket and just sort of looked confused. There are always the performance artists who do ritual crying/touching/humming dances. I prefer to move away quickly because I don't know what to do and funerals creep me out. I figure the quicker I get out of the way, the quicker the ceremony ends. What should people do?

Last note, at one funeral, my then 7 month old son passed copious amounts of stool that left a fragrant and flagrant trail of tears. So basically, I walked right in and right out of the church, to keep my son's BM from waking up my uncle. I knew exactly what to do then.