If you can’t connect to an AirPort network, and the network requires a password that you’ve tried to enter correctly, try the following:

1. Open the Console utility in your Utilities folder.
2. Choose File > Open System Log.
3. Look for a line that includes the message:
kernel[0]: AirPort: Rx’d mesg P-1
4. If the message is there*, try the steps that follow.
5. Open System Preferences, and click Network.
6. Edit AirPort. (If you see the Network Status list, double-click AirPort.)
7. You might have AirPort set to “By default, join: A Specific Network.” Confirm that the network name is correct.
8. Here’s the important part. Re-enter the network password.
9. Click Apply Now. (Don’t change your Location before clicking Apply Now, or your changes probably won’t be saved.)

*If you aren’t getting that error, I don’t know what the problem is. This tip won’t help you if you’re trying to get into a network where you don’t know the password.

If you’re in the middle of dragging a file or other object, you can press the Esc key to cancel the drag without having to remember where you dragged from. After you press Esc, you’ll see an animation of the dragged icon jumping back to its original location. This is especially useful when the original window location is out of view, which can happen due to the autoscrolling and spring-loaded folders that OS X provides when you drag. The reason Esc trick is better than just letting to is that when the original location is out of view, letting go of the mouse button might drop the icon somewhere other than the original location or the intended destination. Esc guarantees that it goes back to where it was.