Use Property List Editor to edit plist files for free
Property List files, or more commonly known as plist files, are basically Mac application specific preference files. They contain information and settings for various applications and are usually in the easily identifiable format of com.developer.Application.plist and located within the /Library/Preferences/ directories.
You can edit these directly and very easily with Apple’s Property List Editor application. Property List Editor comes as part of Apple’s Developer Tools X Code package and is well worth downloading.
If for whatever reason you don’t want to download Apple’s XCode and Property List Editor app, you can try Pref Setter, which is another free plist editor solution.

I was looking for a plist editor a while ago and had a hard time getting anything worthwhile that was free, finally I came across Apple. It amuses me that developers charge for plist editors when Apple has one for free like this, I guess suckers are quickly parted with their money!
I just wish PLE provided some sort of search capability.
[...] By default Gmail Notifier does not have a value set for AutocheckInterval, which can lead to extended lengths of time between email checking (hours if you’re away from your computer, and regularly 30+ minutes while at your Mac). You can also just manually adjust this setting by adding the value in a Plist editor. [...]
[...] is also the option of manually creating the plist file, either though a plist editor or if you’re familiar with plists just by using a text [...]
What a ..just downloaded Xcode 4 but can’t find no trace of Property List Editor application. So where did that app. go to?
Grtz.
Here’s a tutorial on how to get the Snow Leopard Property List Editor app working on Lion with XCode 4.
http://sveinbjorn.org/install_property_list_editor_app_on_mac_os_x_lion
I followed the instructions in the sveinbjorn.org link, but could not make things work on my new Macbook Air running 10.7.4. I needed extra files in the Developer/Library/PrivateFrameworks folder. I copied the following to the root level of my Lion drive from an XCode 3.2.6 installation on a Snow Leopard volume (had previously downloaded XCode from Apple developer site):
/Developer/Applications/Utilities/Property List Editor
/Developer/Library/PrivateFrameworks/DevToolsBundleInjection.framework
/Developer/Library/PrivateFrameworks/DevToolsCore.framework
/Developer/Library/PrivateFrameworks/DevToolsCParsing.framework
/Developer/Library/PrivateFrameworks/DevToolsFoundation.framework
/Developer/Library/PrivateFrameworks/DevToolsInterface.framework
/Developer/Library/PrivateFrameworks/DevToolsKit.framework
/Developer/Library/PrivateFrameworks/DevToolsRemoteClient.framework
/Developer/Library/PrivateFrameworks/DevToolsSupport.framework
/Developer/Library/PrivateFrameworks/JavaKit.framework
/Developer/Library/PrivateFrameworks/PlistEdit.framework
It’s possible I didn’t need all of these, but I got error messages saying I needed JavaKit.framework, DevToolsCore.framework and DevToolsFoundation.framework, so I guessed at what might be necessary and didn’t bother to eliminate any others.
Why install ALL of XCode, when you can download just the plist editor, there are free ones that do the job. Beats installing the xcode monster on a users macbook pro just to work around LDAP problems caused by Apples infinite wisdom…