Here's a quick nifty little tip for a problem I encountered. I am the sort of person who has iTunes running 24/7, whether or not I'm listening to music. So, I very rarely ever quit iTunes, except when there is a software update for it. However, there is always this problem that when I quit iTunes, it automatically starts back up. This is extremely annoying.
A solution to this problem is that any time you want to quit iTunes and not have it start back up, open up Activity Monitor and search for the process genredetection. Quit this, and iTunes should then behave properly and quietly quit when you want it to.
[robg adds: This tip appears (with more detail and screenshots) in this post in the author's blog. As I wasn't experiencing this problem, and didn't have a process named genredetection, I went digging for the cause, and found this thread on the Apple Discussions (which referenced a post from MacUpdate). It turns out that the genredetection process comes from the SRS iWOW plug-in, and it's supposed to quit if iTunes quits normally. It seems, at least in some cases, that's not the case. An alternative solution then is to disable the plug-in when you need to quit iTunes.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090411171843370