Problem debugging my app with xcode

I'm developing an app that download news from google reader. The app works perfect on the iphone simulator but when I try It on my phone the app crash when I try to get news from other source(The app reload news and parse xml document). The problem is that I can receive info about the problem because it crash before while in the simulator it works perfect. So my question is How can I debug to get some info about?. Probably the problem is that the device has not so much memory... But I'm not sure and I wan't to know some more info. Which struments I can use? Instrument? P.S. I'm using xcode 4

**EDIT! I can't undestand error... I tried with instruments... In your opinion if the app works perfect in the simulator but crashes after the reload of some news (after 2 times) what kind of error could be?

**EDIT I obtain more info about:

Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: -[GoogleReader feedParser:didParseFeedItem:]
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: MWFeedItem: “Apple Tv e Spotify: Combinazione vincente” - 2011-07-20 09:37:17 +0000
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: -[GoogleReader feedParser:didParseFeedItem:]
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: MWFeedItem: “Partecipa al concorso Original iPhone Film Festiv…” - 2011-07-20 08:58:54 +0000
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: -[GoogleReader feedParser:didParseFeedItem:]
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: MWFeedItem: “Arriva Roku 2” - 2011-07-20 07:57:13 +0000
Sep  6 23:06:13 unknown NewsPad[2534] <Warning>: -[GoogleReader feedParserDidFinish:]
Sep  6 23:06:14 unknown MobileMail[2503] <Warning>: Received memory warning.
Sep  6 23:06:14 unknown SpringBoard[15] <Warning>: Received memory warning.
Sep  6 23:06:15 unknown UserEventAgent[12] <Notice>: jetsam: kernel t开发者_如何学Goermination snapshot being created
Sep  6 23:06:15 unknown com.apple.launchd[1] <Notice>: (UIKitApplication:com.apple.mobilemail[0x774d]) Exited: Killed: 9
Sep  6 23:06:15 unknown com.apple.launchd[1] <Notice>: (UIKitApplication:com.apple.mobilephone[0xffde]) Exited: Killed: 9
Sep  6 23:06:15 unknown SpringBoard[15] <Warning>: Application 'Mail' exited abnormally with signal 9: Killed: 9
Sep  6 23:06:15 unknown com.apple.launchd[1] <Notice>: (UIKitApplication:com.PaoloSmedile.NewsPad[0x69e6]) Exited: Killed: 9
Sep  6 23:06:16 unknown SpringBoard[15] <Warning>: Application 'Telefono' exited abnormally with signal 9: Killed: 9
Sep  6 23:06:16 unknown SpringBoard[15] <Warning>: Application 'NewsPad' exited abnormally with signal 9: Killed: 9
Sep  6 23:06:17 unknown kernel[0] <Debug>: launchd[2540] Builtin profile: MobileMail (sandbox)
Sep  6 23:06:17 unknown ReportCrash[2539] <Error>: Saved crashreport to /Library/Logs/CrashReporter/LowMemory-2011-09-06-230617.plist using uid: 0 gid: 0, synthetic_euid: 0 egid: 0

What I must do?

In the Organizer you can get the device log of the crash and also see the console from the device.

Also you might try simulating memory warnings in the simulator.

In Xcode in Edit Scheme under options turn on the memory warnings, but Zombies only for the simulator.

Compile your app with the Analyzer and fix all warnings.

Set breakpoints on exceptions and reproduce while running your app on your device in the Xcode debugger.