If you plug in your iPad/iPhone/iPod then iPhoto or some proprietary image transfer application automatically opens even if you don't want it to, because the device is regarded as a camera.
You can change this behavior by using Apple's Image Capture utility to set defaults for each device.
This problem has been plaguing me for a while. I have a Nikon DSLR, a Canon Point and Shoot, an iPad, an iPod touch, and now an iPhone. All of them are treated as cameras when I connect them via USB.
I frequently use Nikon Transfer to move images from the Nikon DSLR, and it always opened no matter which of these devices I connected. The preferences in Nikon Transfer don't help, and the options in each of my iDevices preferences gave me nothing to manage this either.
So, when I was digging through Image Capture (it's in /Applications) to decide how to handle my new iPhone's images, I found a device list on the left, and options to change what app would open when you attached them. Once can even determine where to move/copy files on the hard drive. I set my iDevices to open no app when connected and now the only thing that opens Nikon Transfer is my DSLR.
[crarko adds: Image Capture is one of those very useful and often overlooked utilities. It's worth getting to know better.]
This hint shows a way to close an application AND its windows.
In Lion Command+Option+Q lets you quit an application and close all of its windows so that when you reopen the app there won't be open windows.
[crarko adds: In Snow Leopard it there are options to close all windows (generally Command+Shift+Option+W) but it's not tied into the Quit operation. I imagine since Lion re-opens all the previous windows when the application launches the new shortcut was added to prevent that.]
This keeps the fullscreen display of Flash videos open on all spaces. Nice for watching streams/videos on a second display (TV) and then switching around.
You'll need a plist-editor like XCode (or just a text editor if you're comfortable with that) and Flash version 10.2 or later, so it remains open when the application focus changes.
First backup and then open the file ~/Library/Preferences/com.apple.dock.plist with your editor.
Add a new line under workspaces-app-bindings
Name it org.mozilla.plugincontainer.
Change the data type to Number.
Set the value to 65544.
Save the file.
Log out and back in.
Works on 10.6. but I cannot check this on Lion, so please do and comment.
[crarko adds: I haven't tested this one. I admit I'm not quite exactly sure what this does, so exercise some prudence. Make sure you do the backup before making changes to the plist file. If you are adventurous and give it a go, do post results in the comments.]
When you use Mail, or another email client, together with a Gmail account you will surely know that clicking on a message and pressing the delete key does remove that message from Inbox folder but leaves a copy of it in the 'All Mail' folder on the Gmail server. Effectively the message has not been deleted. This is the default Gmail behavior.
While I like using Mail.app with Gmail I don't like the 'All Mail' folder. Here's how to configure Mail so a deleted message ends up in the Trash folder on the Gmail server.
In Mail.app, under Preferences click the Accounts icon. Select your Gmail account. In the Trash section check the box 'Move deleted messages to the Trash mailbox' and check the box 'Store deleted messages on the server'. Close the Mail.app Preferences.
On the left side where the Mailboxes are located, expand the Gmail folder, and click on the Trash folder. Next, from the Mail.app menu select Mailbox » Use this Mailbox For » Trash.
Now messages you delete in Mail.app will from now on be moved to the Trash folder where you can permanently delete them by selecting them and pressing the Delete button on your keyboard or by enabling the automatically delete after x number days setting in Mail.app preferences.
I hope you find this hint useful. It's tested on Mac OS 10.7.2 Mail 5.1.
[crarko adds: It looks to me that these options are available in 10.6.8 Mail as well, although I haven't verified that it works the same.]
You can manipulate Collada (.dae) 3D objects in Lion.
I was converting a Sketchup 3D file to Collada to be able to open it in Cinema 4D when I noticed the Finder icon generated was looking same as the model. I could Quick Look at the file and discovered that you can manipulate the whole 3D right into Quick Look, or Preview.
[crarko adds: I haven't tested this one. The file type is one that is used for a lot of interchangeable 3-D graphics modeling in various game engines.
According to several comments, this also works in Snow Leopard.]
After upgrading to Mac OS X Lion, I started searching for mail to find registration emails for software that I had to reinstall. I knew they were in my mailboxes because I had found them with no problem in my previous Snow Leopard Install. None of the emails were showing up when I did a search via Lion's search function.
After doing a search I found a thread on Apple Discussions that helped solved the problem but I went back to search for the thread so I thought I'd submit it as a hint.
The solution is to force Spotlight to re-index your hard drive. There are a few ways you can do this:
In previous versions of iCal, calendar items and to-do items (reminders) were contained in the same calendar container. In Lion, they are separated into Calendars and Reminders Lists.
To see the Reminders Lists, click on the word 'Reminders' above the list of reminder items on the right side of the screen. To create a new Reminders List, select File » New Reminders List.
You may have a Calendar and a Reminders List with the same name. But you can also have Calendars and Reminders Lists which are only displayed in the one place.
When I upgraded from MobileMe to iCloud, I thought some of my calendars had disappeared, except the reminders from those calendars still appeared in the list. These were special calendars I had that only contained reminders. Then I clicked on 'Reminders' and discovered that they were listed separately.
More of an observation than hint but from the Apple site (and Geniuses at the stores), I was expecting to have to move photos taken on my iPhone from Photostream to the permanent library on the iPhone to preserve them after the 30 day limit.
Not so. Both on my iPhone and my iCloud-synced MacBook Air, the photos are both in Photostream and in the Library automatically. Personally, I think this is preferred behavior but does seem to defeat Apple's goal of not having too many pics stored on the iDevices.
[crarko adds: I haven't tried Photostream as part of my general putting-off of the iCloud transfer, but the behavior mentioned here is what I would expect, and would have been pretty annoyed has it been otherwise. You should never be forced to do these things manually.]
It looks like you can finally hide purchases from the the App Store (and the iTunes store).
This may have been mentioned somewhere before, but I haven't seen it.
If you open iTunes and go to the iTunes store and click on 'purchased,' you'll get your list of purchases. From here, if you mouseover a particular purchase (movie, tv show, app), you'll see a little X in the top left corner. If you click on the X, you'll see a message: 'Are you sure you want to hide this purchase? You can unhide purchases from your Account Information page.'
Click the X and the purchase is now hidden on all your Apple devices.
[crarko adds: I don't know how new this is, but I'd not noticed it before either. Handy to know for things like the MLB app that have a new version each year.]