Using body langauages ..When do  I figure out that the wife is in for a good time ?and when the opposite?
Her body language is most likely due to something you say. So make sure that about a week before you want a "good time" you dont say anything like:\n1. That dress makes your butt look fat\n2. I hate your mother\n3. YOU SPENT HOW MUCH ON SHOES?!?\n\nThose are just a couple that keep me out of the dog house. I'm sure there are thousands more. Sometimes every other word will offend her and you know what that time is so it will be best to wait a week for the "good time" and really it's best to just avoid her for that whole week.
You can never really tell.  Knowing a little of their past history & dealings (their track record), their personality, and what is important to them can help. \n\nYou might be interested in game theory and neuroeconomics.  A recent neuroeconomic study looked at the effect of oxytocin (a hormone) on trust relationships.\n\nPeople who took a squirt of oxytocin up the nose were more likely to trust others with money.  Oxytocin is heavily released by females during orgasm and childbirth.  So a woman who orgasms frequently and bears your child may be biologically attuned to trusting you.