This tip solves a problem that I've experienced myself and many of my clients have complained about - laptops waking from sleep while in their cases because the latch won't keep the lid closed. This can cause overheating, which can lead to a variety of other problems, like hard drive failures, etc. My solution is, of course, to fix the latch! But there are times when that isn't convenient and even if it's convenient it doesn't happen often enough for some people to even bother stressing about it. By harnessing the power of pmset, the command line app that controls power management settings, you can fix it so that your sleeping beauty stays asleep, even when the latch isn't doing its job.
The command is an easy one - a single line. Ready for it?
sudo pmset lidwake 0
By setting the lidwake value to 0 you prevent the machine from waking until you tap a key on your keyboard, and since the value gets written just to a plist file, it takes hold right away. Of course you'll need administrator privileges since you'll be asked for an admin password before the command is executed.
For more pmset options, have a look at the "man" pages at Apple's Darwin Reference library, or open your Terminal and type "man" (without the quotes), hit return and then type "pmset" (without the quotes.)