Principles are general ideas. They explain why you do things a certain way, that is, they explain patterns. Take the sewing and woodworking pattern "measure twice, cut once." Why do that? Because of the principle "materials are expensive, and shouldn't be wasted." (OK, that's a pretty obvious principle.)
Here are principles on this website.
Break a task into smaller tasks, do each smaller task, and put them back together.
|Pattern||Sales report, Multiway|
Write a little code, then test it. Write a little more code, then test it.
|Debugging||Avoiding bugs, Sales report|
|Read code actively||
When code doesn't work, the first thing to do is carefully read through the code.
Start by understanding a program's goal, then work backwards.