Predict
Read the code. What do you think is going to happen?
Run
Run it! See if you were correct.
Investigate
Why were you right or wrong? See if you can work out what happened at all levels. Do you understand every line? What about the relationship between the lines, the order of operations and the entire program function as a whole?
Modify
Make some changes. Try stuff. What happens if I change that? Can I remove that and it will still work?
Make
Play with it. Add to it or use previous knowledge to extend the code to provide new or different function.
Unreal Engine 4 provides two toolsets for programmers which can also be used in tandem to accelerate development workflows. New gameplay classes, Slate and Canvas user interface elements, and editor functionality can be written with C++, and all changes will be reflected in Unreal Editor after compiling with either Visual Studio or XCode. The Blueprint visual scripting system is a robust tool which enables classes to be created in-editor through wiring together function blocks and property references.
C++ classes can be used as a base for Blueprint classes, and in this way programmers can set up fundamental gameplay classes that are then sub-classed and iterated on by level designers.