Know what a commercial pilot can and cannot do. Thats one of the biggest differences between a private and commercial pilot. Also, what a commercial pilot cannot do without an instrument rating.
Also as a tip, this was common with our examiners but maybe not with all, when you plan your XC, still give plenty of buffer room/fudge factor... but maybe not as much as you did on your private (if you did a lot). As a commercial pilot, being more accurate with numbers is good for business.