Classic:" when the power starts increasing press the B button when it is 100%. An easier way is to press and hold B earlier and release it when it is at 100%. This will increase your digimon's attack stat by 1 and reduce weight. If you fail because you missed 100%, attack will not increase but weight will still decrease. Note that there is no way to determine your digimon's attack stat.
"Pendulum:" Use this to determine your digimon's 'critical number'. This is the number if times you need to shake your digimon device (phone) to get a mega hit. The critical number will be 2-9. It will always be the same. When the screen says COUNT, if you shake the phone the correct number of times you will score between 1 and 5 mega hits and your attack stat will increase correspondingly. Use trial and error to determine critical number. The critical number will likely change when it evolves though. Also, it can be a different number for the same type of digimon (eg your friend's metalgreymon can be different to your metalgreymon)"
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Read more: http://digimonunlimited.proboards.com/thread/449?page=1#ixzz2liFeQRJw