Constantly Observe the Flow of Your Program and the Modification of Its Data

Constantly Observe the Flow of Your Program and the Modification of Its Data

This is very important! If you have designed and written your program carefully, you should know, from watching the output, exactly which section of code is being executed and what the contents of the various variable are. Obviously, if your program is behaving incorrectly, this is not the case. There is little else to do but either use a debugger or fill your program with print statements and watch the flow of control and the contents of important variables.