I was asking how you personally can distinguish between one of those laws that must be followed, and one of those laws that it's ok to break.
By reading The Catechism of the Catholic Church.
The quick answer, nowhere near complete, is that Jesus came to fulfill the ceremonial laws by being the "final" sacrifice for your sins. Christ did not do away with the moral laws, which should still be kept.
So, don't murder still holds. Don't commit adultery (sorry slick Billy C.) still holds. If you do commit a sin having to hop up and down on one foot 100 times then do 25 back flips (ceremonial) can be disregarded (OK, that's wasn't one of the ceremonial laws but I think you get my point).