You need a damage source (bomb, enemy, i.e)
This is how I do my megaflips, it's pretty easy, with enough practice you can get an 90% consistancy!
Steps for Megaflip (backwards)
1- Pull out a bomb and shield drop (Holding L and R)
2- Backwalk away from the bomb, until the Action Icon says Attack (still holding L and R)
3- Ok now timings pretty hard at first, when the bomb starts to speed up and flashes blue and pink at a faster pace (Just about when the bomb is aobut to explode), you Roll (Still Holding L and R)
4- While your rolling (you should be starting to get near to the end of the roll), The bomb should explode.
5- When the bomb explodes, and starts to hit you (shields blocking you from getting hit) BACKFLIP.
6- You should be backflipping a longer distance AND Higher.
NOTE: you can also Mega Sidehop, same steps as above, BUT you don't backflip just sidehop.
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You can also Megaflip / Damage boost. Harder BUT used to get onto Gerudo's Gate to Fortress.
Steps for this technique!
1- On the bridge, go right next to a stake (still on the bridge NOT STAKES) now go opposite of the gate (walk towards the entrace of Hyrule Field) GO ABOUT 3 BRIDGE PLATFORMS. (The wooden lines? on the bridge, you can tell which is one by the little gaps in the bridge)
2- Pull out a bomb, and shield drop. NOW PULL OUT ANOTHER BOMB RIGHT AWAY, TURN AROUND, AND THROW IT AT THE GATE WITHOUT MOVING A LOT.
3- The 2nd bomb should hit the gate and go right infront of it.
4- back away from the shield dropped bomb, and then megaflip TOWARDS THE 2ND BOMB, AND WHILE YOUR MEGAFLIPPING, LET GO OF R.
5- When you reach the 2nd bomb, it should explode, and you will be damageboosted OVER OR ONTO the gate. Don't let the guards see you and make your way into Gerudo's Fortress!
Note: the regular method was hard for me, (shield dropping a bomb, backwalking, placing a bomb right by the gate, going to the first and megaflipping. The timings so hard and very hard to roll without talking to the Gerudo.)
http://www.youtube.com/watch?v=j33uZRmglS8 <~ this is what i mean.
But it's Pokey's trick, so it's his credit.