If you press and hold one of the apps (any one) they should start to shake. You can then :
- press the 'x' in the top left corner to delete them (you cannot delete Apple's built-in apps such as iPod, App Store, YouTube etc). If you don't see 'x' on any of the downloaded apps then check that Settings > General > Restrictions > Deleting Apps isn't off
- rearrange their order by dragging one to a different place on the screen (you cannot leave blank spaces between apps on a screen)
- create a folder by dragging and then holding one app on top of another. You can then rename the folder if you want to (folder renaming can be done whilst the apps are shaking)
- add an app to a folder by dragging an app so that it is on top of a folder
- move an app to a differrent homescreen by dragging it so that it overhangs the edge of the screen; after a second or two the screen should then display the next or previous screen (depending on which side of the screen you are holding it)
When you've finished press the home button so as to stop the shaking.
You can also do all of this when connected to your computer's iTunes, via the device's apps tab and the images of the iPads screen(s) (the changes don't take affect until you sync the changes to the iPad). Some people find this way easier.