Q:

What are your naming conventions for Objective-C "private" methods? 

Inheriting code from other developers has made me a firm believer in keeping as many messages as possible out of a class' public interface by means of a Class Extension.  I'm also a firm believer in adopting special naming conventions for private, implementation-specific members of a class.  I really like being able to tell at a glance what messages being sent and what members being referenced within the implementation context are not ever intended for public use and vice versa.  If nothing else, it makes the overall semantics of a class easier for me grasp more quickly, and that's worth it. 
Justification aside, I've written boatloads of classes with boatloads2 of private methods, but I've never really come up with a pattern for naming that I really love (like I do the controversial ivar_ convention for ivars).  Notable examples:
@interface myClass()

// I like this, but as we all know, Apple has dibs on this one, 
// and method name collisions are nasty. 
- (void)_myPrivateMessage;

// The suffix version promoted by Google for ivars doesn't really translate
// well to method names in Objective-C, because of the way the method
// signature can be broken into several parts. 
- (void)doWork_; // That's okay...
- (void)doWork_:(id)work with_:(id)something; // That's just ugly and tedious...
- (void)doWork_:(id)work with_:(id)something and_:(id)another; // My eyes...

// This version is suggested by Apple, and has the benefit of being officially 
// recommended.  Alas, I don't like it: The capital letter is ugly.  I don't like 
// underscores in the middle of the name.  Worst of all, I have to type three characters 
// before code-sense does anything more useful than inform me that I am typing. 
- (void)BF_doWork;

@end

At this point, there are a kajillion different means by which I could mangle my private method names, but instead of making something up, I figured I would first take a poll for any popular conventions I may not be aware of.  So, what have you used? 

A:

I don't distinguish private methods by name.  Instead, I keep them out of the public interface by declaring them in the class extension portion of the .m file, thus:
@interface MyClass ()
- (void)doWork;
@end

A:

I use double underscore for my private methods:
- (void)__doSomethingPrivate;

It almost looks like the single underscore-syntax (good readable) and at the same time confirms to the Apple guides. 

A:

I use a prefix, no underscore.    The prefix is generally related to the name of the project in question.   If you do use underscores, there's no need to have more than one.