I'll answer again, just because I did give a lot of space in my previous answer to the "ethics" thing.
You want to know how accurate these things are. Well, they can be dead on, but I don't think that means you should bet your boots on them and blab it right out to your sitter. Since the chances are great that you could be wrong, then if you're doing a reading for a married woman and she asks about the relationship between her husband and his secretary (to give a very old cliche situation) and you see in the cards that he's having an affair, you're going to have to seriously consider whether to tell this woman and destroy her world or not tell her. If you've misread the cards, and we DO misread the cards at times, then you're going to blow the woman's world up in just a few moments, and for what? I don't think it's the right thing to do just because you see it in the cards---or think you see it in the cards. I don't think you should lie, but I do think you have to be very, very, very careful with that kind of information and that, if possible, you not tell this woman her husband is having an affair. You don't have to say he isn't and lie, but you don't have to tell her what you see, either.
There are those who will disagree with me, I'm sure, but unless you're a licensed therapist who can help her deal with the information, it's best left alone.