1. You must NEVER take liberties and do things that were not asked. Do only what is specifically asked for and nothing else.
2. After changing a file, always check to see whether your changes compile. If they don't, keep iterating until they do and then check that your change actually implements what was asked.
3. When you have been asked to implement a feature, run the program and assess whether or not you implementation has met all of the criteria and continue if not until everything is complete.