Learn the tapping section of eruption, that will get you going, then move across strings by learning a few Vai pieces (Big Trouble from his time with DLR or Shyboy are great examples) then look at Greg Howe for some great tapping ideas that are more scaleular .
Tabs for all of them can be found at www.powertabs.net
Don't forget that like everything else there are many ways to tap ie. using your index finger or middle finger or pick etc. experiment and find what you like and always keep the door open to try diferent ways to acheive what you want
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