How to get apk for Installed Android App

I was trying to get apk for installed apps on adroid and question was.
- where are the apk files stored on android phone
- How to Download APK files from Android Market to PC

Solution 1: For Rooted Phone
      Preinstalled applications are in /system/app folder. User installed applications are in /data/app. I guess you can't access unless you have a rooted phone. 

Solution 2: Non Rooted Phone
      If you just want to get .apk file of something you previously installed just do this:
     1. get AirDroid from Market (Google Play)
     2. access you phone using AirDroid from your PC web browser
     3. go to Apps, select preinstalled or installed app
     4. click 'download' button to downlaod .apk version of this app from you phone
you don't have to root your phone or use adb tool.

Solution 3: Non Rooted Phone
    1. Install Root Explorer or ES file explorer
    2. take backup of apps
    3. and you can find apps in /apps/backup/

Solution 4: Using Apk Downloader tool 
           Follow from here..