theblackjack

ok, Welson... this is how you do...
1st: back up your old iPhone(example: Welson's iPhone) in iTunes.....

2nd: connect new iPhone 4 to iTunes, it will ask u to set as new phone or restore from....select a file name (Welson's iPhone) and restore it.....

3rd: go to your old iPhone,Setting>Reset>Erase All Content and Setting, it will erase everything inside your old iPhone....

hope this will help you, welsonwong....Cheers....