If you regularly use specific applications, or access certain documents or locations in OS X, you can take advantage of the system's log-in items feature to make these items available to you whenever you log in to your system. For instance, folks who regularly use Mail and Safari might wish to have these programs open automatically when they log in. While launching applications is the most common use of the log-in item list, it can be used for quite a bit more.
Setting up log-in items
Setting up and managing log-in items is easy. To do it, go to the "Accounts" system preferences and select your account. Then click the "Login Items" tab and you should see the list of items that are opened when you log in to your system.
The log-in items you see will be different for each system and user, but are managed in the same way. To add an item to the list, just drag it there or use the plus button at the bottom of the list. Conversely, to remove an item you can drag it out of the list or use the minus button. You can also right-click applications on the Dock and then use the Options menu to select "Open at Login" for that application.
When items are in the list you can check the "Hide" button, which will invoke the system's "Hide" feature on the application once opened, so it is not cluttering your desktop. This is particularly useful if you have a number of tools that you regularly run which you may not immediately need, but you would like to have open and available. The order of items in the log-in items list does not matter, as they will all be launched at the same time and ultimately open at their own pace.
The log-in items list is fairly straightforward with no extra settings or features; however, you can take advantage of it by adding a number of uncommon items to the list:
Applications--The most obvious addition are applications you commonly use.
Preference Panes--If you regularly use specific system preferences, you can go to the /Macintosh HD/System/Library/PreferencePanes/ folder and add the one you would like to the list. This will open the system preferences to that pane at log-in (you can only do this for one preference pane item).
Documents--Any document on your system can be added so it will open by the default program assigned to handle it. Images, text files, Word files, PDFs, and other common types can be added, but in addition you can add disk images so they will automatically mount, and also add URL pointers. To create a URL pointer, go to a desired Web page in Safari and then drag the address from the address bar to your desktop or another Finder window. The link will be created there, and can then be added to the log-in items list.
Folders--As with documents, if you add a folder to the list it will also open and display its contents. This in itself may not be much use, but you can use it to automatically mount commonly accessed networked shares on the system, including FTP sites. First connect to your network location, and then drag a folder within that location to the log-in items window. Then when you log into your system the Finder will automatically connect to the network share.
What not to remove
While the log-in items are useful, the list may contain a few items you should not remove. These usually are "Helper" applications that add functionality to third-party applications. For instance, antivirus programs may have tools that automatically launch for your log-in session, and media handler helpers may be installed by programs to add options for managing certain CDs and DVDs.
These programs provide services that run during your log-in session, and while removing them can prevent these feature from working, they usually can be added back at a later date (usually by opening the respective application again); however, it can sometimes be cumbersome to locate and add a helper utility again so unless you absolutely do not need a particular log-in item then it may be best to keep them.