Before you flash a rom You have probably installed a number of apps.
When you flash a rom all of them will be gone. Only the apps included by the dev will be there.
You can't change that but you can backup your apps so they are all in one place and you don't need to search for them or have a working market.
There are a number of apps you can use but many of you will already have the ES File Manager so this will use it.
If you don't have it you can get it here.
Turn off as many apps as you can. Some apps will not backup while running.
When you open it you are normally in the file manager mode.
Tap the second icon from the right to switch to Application mode.
Do a long press on an icon. Tap select all.
Now press menu then tap backup
The backup begins you can see how it is going by opening the notification bar
Note take an app failed to backup. This is an app that won't back up while running.
There will be a quick message when backup is done and the notication bar will no longer have apps backing up.
In the File manager Tap the second icon from the right to go back to file manager. open backup/apps and there they are.