It takes a bit longer, but a better alternative is often to file a detailed Bug Report to Apple:

This requires a membership in the Apple Developer Connection, but you can get one for free  (and if you already have an Apple ID, you can use it).

1. •Register here: Apple Developer Registration.
   

2. •Once you receive the confirmation email, go to the Bug Reporter site and login.
   

3. •Click New Problem at the top.
   

4. •Click Help at the top, and/or any of the items underlined in blue, for more information.
   

5. •Provide as much specific detail as possible, and attach a log, screenshot, etc., if appropriate, in the lower section.
   

6. •When done, click Submit at the bottom.
   

The more specific and detailed your report, the better chance of Apple finding and fixing the problem.

Apple may contact you for more information, or send an e-mail telling you the problem has already been reported.  You may or may not be notified if/when they fix it.

To just make a report, the easiest way is Apple’s  Feedback  site, but it’s pretty general, and hard to provide the kind of detail that Apple’s engineers can use to "home in" on the problem so they can reproduce and fix it.

That’s also the place for suggestions and enhancement requests.

But you won’t ever get a response, so it’s hard to tell if/when something is really wrong, much less whether it will ever get fixed.

If that isn't possible or convenient, or doesn't apply, usually, the best way is to call AppleCare: 

1. U.S. iPod, Mac and iPad technical support: (800) APL-CARE (800-275-2273). 
   

2. 
   

3. Elsewhere, see:  Contacting Apple for Support and Service
   

If your Mac is less than 90 days old, or you have the optional 3-year AppleCare coverage, the call is free.  Otherwise you’ll be charged (about $50 in the U.S.).

The AppleCare folks can usually determine fairly quickly if it’s an already-reported problem, and if there’s a workaround, supply it, or an alternative.

If not, they’ll assign a Case Number, and work with you to diagnose it.  They may walk you through various procedures, and perhaps e-mail you a "Capture Data" app to extract pertinent information from your Mac that you can e-mail back.

They may do some research and call or e-mail back for more information, or to report the results of their testing.  If they determine that it is a problem, and they can reproduce it, they’ll consult and follow-up with the appropriate Apple software engineers, and escalate to higher levels if necessary.

Unfortunately, though, they won’t tell you how, when, or if it’s going to be fixed, or notify you when it is.

If you're near an Apple Store or Apple Authorized Service Provider, and can take your Mac to it, that's usually best.  There's no charge unless they have to replace parts or keep it for diagnosis (and of course, if it's within the 1-year warranty or you bought the optional 3-year AppleCare coverage, there's no charge for repairs unless they're caused by damage).

If the problem involves a peripheral, such as an external HD, Time Capsule, etc., you'll need to take it along, too.

Use this link to make an appointment at the Genius Bar:  http://www.apple.com/retail/geniusbar/

Or this one to find an Apple Authorized Service Provider: https://locate.apple.com/country  Select your country, then click the Service box.