Consistent instructions and examples

I started off with "hints" that required the poor student to piece
together the information from incomplete bits. A complete example is
like a picture that is worth 1000 words and far clearer.

01_hello.zig

@@ -2,11 +2,17 @@
 // Oh no! This program is supposed to print "Hello world!" but it needs
 // your help!
 //
-// Hint: Zig functions are private by default.
-//       The main() function should be public.
-//       Declare a public function with "pub fn ..."
+// 
+// Zig functions are private by default but the main() function should
+// be public.
 //
-// Try to fix the program and run `ziglings` to see if it passes.
+// A function is declared public with the "pub" statement like so:
+//
+//     pub fn foo() void {
+//         ...
+//     }
+//
+// Try to fix the program and run `ziglings` to see if it works!
 //
 const std = @import("std");