Showing logs it’s the most important think that you must learn while developing in any language.

Of course there’s a lot of methods, showing something in the screen, code breakpoints and write a log of what you are doing.

For doing it in Objetive C:

NSLog(@"This will be in the log");

Of course, the @ symbol means that after that will be a string but you can show any variable in this form:

NSLog(@"This will be in the log %@", variable);

Where the % means that will be changed with the variable.