How to correctly set the minimum iOS version for my app?

I am developed one application in ios 4.2. I try to test that application in iphone 3g. In that process error will occur like

"The Info.plist for application at /Users/gvrao/Desktop/BabyCryApp/build/Debug-iphoneos/BabyCryApp.app specifies a minimum OS version of 4.2, which is too high to be installed on iphone 3g"

And change the version in iphone development target to 3.1.3. But it was not working. Please tell me how to solve this problem.

You need to set the Deployment target in the build settings to the minimum iOS version you require.

A general guideline is to set:

• Base SDK to latest
• deployment target to the minimum version you support.

Also - check your Info.plist file for the MinimumOSVersion key.