I just asked my doctor a question about this today.
She said they tell people who have herpes not to be sexual or have sexual contact if they have an outbreak (very obvious to sexual partner) or when they are having burning, tingling (not obvious to sexual partner) and something else that is associated with herpes when they are going to break out. (I can't remember what the third sign was)
I asked her about viral shedding (as I have heard other people talk about it) and she said that is VERY rare but it is when a person who has herpes can spread the virus without having any signs at all. But she emphasized it is VERY RARE. And again she said they just tell people who have the virus to watch for the burning etc and, of course, the actual outbreaks, and refrain from sexual activities during that time.
Also (from my own research) condoms will NOT protect you from herpes as the herpes outbreak is usually outside the area covered by condoms. That is why you and your partner should feel comfortable 'checking' each other out.