Welcome back to Mac 101, our series of posts aimed at novice Mac users and veterans who like the occasional refresher.

If you've owned a Mac portable for any length of time, chances are pretty high that you have had your Mac wake up while stowed away in a carrying case. You know the drill as well as I do. As soon as you open your bag of choice, a wave of heat rushes up to your face. And that's when you realize your Mac isn't sleeping and your battery is now mostly dead.

For our friends who are new to the Mac or who may have never used the sleep mode you might be asking yourself why it is important. For road warriors who office at Starbucks or just those that are energy conscientious, it is actually quite impressive functionality. Sleep mode is a low power, energy-saving mode that your Mac uses to extend the life of both batteries and displays. While it's more useful for mobile machines, Sleep mode is available on both portables and desktops.

Sleep mode on the Mac is very similar to system standby in Windows. It is is almost always successful at saving my battery life so when I'm on the road I don't have to worry about opening my Mac to a dead or dying battery.

How does one take advantage of all of this sleepy goodness? Well, there are several ways, some of which depend on your personal configuration. The most common method for putting your Mac portable to sleep (no, not like that) is simply by closing the lid.

Pressing the power button results in a dialog box with buttons for sleeping, restarting, or shutting down your Mac -- click Sleep, or press the S key to select the Sleep button. You can also change your system preferences to make the power button sleep your Mac with a single press.

Simply choosing "Sleep" from the Apple menu will also send your Mac to dream-town. Another neat trick: if your Mac has an infrared (IR) port you can use your Apple Remote to put your computer to sleep. Hold the Play/Pause button to put your Mac to sleep and push any button to wake it back up.

As it turns out, Sleep mode does not always work as expected. If you've had trouble with your Mac waking up without your being aware, you're not alone. In fact, there are several reasons why your Mac might wake up in transit without warning. Apple has even seen-fit to create a support article on the very subject. Three of the more common causes of sleep failure (besides Caffeine) are:

1. External hard drives not properly dismounted prior to sleeping
2. Bluetooth devices (such as a portable mouse) waking the Mac up
3. An active application preventing sleep such as iTunes or QuickTime

Regarding external hard drives, I have found that a drive needs to be unmounted & unplugged prior to putting your Mac to sleep. This prevents the majority of sleep issues caused by external hard drives. Another good idea is to disable the "Allow Bluetooth devices to wake this computer" checkbox in Bluetooth System Preferences. A simple step with a powerful outcome -- no longer will your portable Bluetooth mouse awaken your Mac from its slumber.

While some people may not find Sleep mode a key bit of functionality in their Mac, many have found that it is absolutely indispensable.

For other awesome beginner tips, visit our Mac 101 category.

One of the things that confused me the most when I switched to the Mac platform was the fact that there's no built-in way to lock the computer manually with a hotkey when walking away from it. This is something that was drilled into me from working in an office full of pranksters where leaving your computer unlocked was virtually a guarantee that you would be hosting a party for all of your co-workers that coming weekend.

It turns out that this is an oversight in Mac OS X, and a 3rd party utility is required to be able to lock your computer with a hotkey. For a simple solution I would suggest installing a very basic preferences pane called LockTight.

LockTight does exactly what you're looking for: assign a specific hotkey that when pressed will lock your Mac, requiring a password to unlock it if you have it configured to require a password to wake from sleep or screen saver (which you should).

Update: Reader Chad reminds us that if you actually want your machine to go to sleep with a keystroke (as opposed to simply locking the screen) you can use the Option-Cmd-Eject key combo.

[via Lifehacker]

Controlling your music while you're working (or playing) on your computer should be virtually seamless. While these days it's almost impossible to buy a keyboard without media keys built-in, there are many users that either don't have media controlling keys on their keyboards, or would simply prefer to keep their hands on the actual keys. While iTunes is not capable of assigning hotkeys on its own, there are a number of iTunes controller applications on the market that can add this functionality.

In my opinion SizzlingKeys deserves to be at the top of the list of iTunes controller apps for its simplicity, reliability, and extra features. SizzlingKeys installs as a preferences pane, and has a very intuitive interface that allows you to choose which functions to enable, and what the hotkeys should be for those functions.

The list of things you can control with hotkeys is fairly comprehensive:

• Play / Pause
• Previous / Next Track
• Volume Down / Up
• Mute / Almost Mute
• Show / Hide iTunes, Playlists, Search
• Set song rating
• Show floater (song information)

In addition SizzlingKeys offers some non-iTunes "extras" that you can control:

• Sleep computer
• Lock computer
• Activate screen saver

The standard version of SizzlingKeys is free, but there is also a Pro version for $5 that includes the ability to skip forwards and back by a customized interval, the ability to toggle shuffle and repeat modes, and the ability to control the system volume.

Quick! The boss is coming! Hide your screen! What, you don't have Spaces set up so you can switch to that handy Excel worksheet you've got open? That's okay -- just put your display to sleep.

Of course, there are other reasons to want to quickly turn off your display, but they all have one simple key combination: Control + Shift + Eject.

It works with both desktop and laptop Macs. Moving the mouse or pressing a key on the keyboard wakes it right back up when you're ready.

Of course, if you want to put your whole computer to sleep, you can use Option + Command + Eject. There are other helpful shortcuts, too, in this article deep in the TUAW archives.

Thanks to our own Michael Rose for this one. Want more tips and tricks like this? Visit TUAW's Mac 101 section.

Everybody needs to sleep, and more than just a few hours each night. It's not just a matter of being in a foul mood all day; there are some pretty serious physiological effects of sleep deprivation. Since you tend to learn the most when you do things incorrectly, I know plenty about lost sleep. Anything that helps my insomnia is worth checking into, so I've spent some time looking at ways my Mac and my iPhone might help me lay down, and stay down. I took a look at the iPhone first; there are more than a few apps available which make me drowsy, but only two that I could find which do it intentionally: aSleep and Ambiance. Fluff your pillow and read on to see how they stack up against each other and a few desktop applications.

• Put the computer to sleep
• Beep
• Stop iTunes
• Start iTunes playing a playlist
• open a file
• repeat the countdown
  

• Sleep = opt + cmd + eject
• Restart = ctrl + cmd + eject
• Shut Down = ctrl + opt + cmd + eject