Name your Arguments

Obscure Objective-C aside that you should never actually take advantage of:

You don't actually need anything between colons in a method signature.

for instance, you could write:

doStuff:arg1 :arg2 :arg3

The method signature would be something like:

- (void) doStuff:(NSString )arg1 :(NSString )arg2 :(BOOL)arg3;

So it's strictly a convention even in Obj-C that arguments are "named".