FB has changed since the making of this video concerning your "App Center Page". Please refer to "Written Instructions" below.

MEGA GIFT EXCHANGE TRICK
This is a way to Exchange one Farm Town Gift for many many more. Although this trick may be used for any Gift item you need and want to fill your Gift Box, it is especially useful for items that you can use the "Store All" feature like Animal Products, Bait, Crops, Fuel, Meats, Sugar, etc. This is because you can continually reload the Farm and Store the Gifts from the Gift Box until the process is finished.
 
It can be quite tricky until you master it, I have had some friends of mine test it out, and it took many patient attempts... but this does work! 
 
This trick does not work on the "MY Requests" tab on your Farm. It only works using the "App Center's Request" page. I have provided the link below for your convenience.
 
READ AND UNDERSTAND THE STEPS BELOW BEFORE ATTEMPTING!
 
1. CLICK HERE TO GO TO YOUR "APP CENTER REQUEST" PAGE OR FOLLOW DIRECTIONS BELOW:
                        
2. ACCEPT A GIFT YOU WANT TO EXCHANGE. "CLICK ON ACCEPT"

3. YOU WILL THEN BE GIVEN THIS OPTION - "CLICK ON CLICK HERE"
4 FROM THE DROP DOWN ARROW "SELECT YOUR GIFT"
5 ON YOUR COMPUTER KEYBOARD "PRESS THE TAB KEY (1) ONCE AND THE BLUE OUTLINE BOX WILL DISAPPEAR.(Tab key is shown in image below)
6
7 HOLD DOWN THE "ENTER" KEY ON YOUR KEYBOARD (in chrome you will see a 1/2 circle spinning) WHEN THE PAGE HAS FINISHED COLLECTING GIFTS YOU WILL SEE THEICON - RELEASE THE "ENTER KEY".

AS SOON AS YOU HOLD DOWN YOUR "ENTER KEY" YOU WILL SEE A PAGE THAT ASKS YOU TO SEND A GIFT BACK TO YOUR FRIEND - YOU CAN DO THIS ONCE THE PAGE HAS STOPPED COLLECTING GIFTS.

AN ADMIN FRIEND OF MINE RECEIVED OVER 300 GIFTS IN APPROX 10 MINS. (Enter key is shown in image below)
8 LOAD YOUR FARM AND EMPTY YOUR GIFT BOX. (I received 99 fuel tanks in just one go
I would like to thank Fred Woloszynek. Fred has given me permission to use this handy little glitch!.