"Simple rules" refers to a set of clear and easy-to-understand instructions or guidelines that help make things easier to follow or understand. Full definition
However, you can minimize the chances of having problems by following a few simple rules of thumb. (smallbusinessesdoitbetter.com)
So stock up on a few key items and follow a few simple rules for how to go casual while still dressing like you mean it during the dog days of summer. (canadianbusiness.com)
A study of how visitors to these sites create descriptions of links suggests that they may be following simple rules without realizing it. (sciencemag.org)