When a person is in fellowship with God, they should be able to follow their spirit enough to know when they are in bounds or out of bounds. I always know when I am at the wrong place at the wrong time by a bad feeling I get.... known as guilt.
I think focusing more on building a relationship with Jesus than wondering if we are doing something wrong is the best way to go. If someone is having a hard time with that in trying to make a decision between right or wrong.... just simply picture Jesus standing next to you and then see if you would do it or not.
I have found Jesus is more concerned with my love walk and my thoughts than he is whether I buy a lottery ticket....or whatever the case may be.