Two rules that have stood me in good stead for a number of years:
1. Always make sure that you can either stop or turn around easily in the distance that you can see in front of you.
2. When flying close to a non stratiform cloudbase, if the cloud a distance away appears to move further down the windshield as you get closer, you are going to go into it. Unless you are equipped, trained, prepared and allowed to go into said cloud - refer to rule 1.