When and where did you dig?

In Pokemon red/blue, You should be able to grab Dig(TM28) in Cerulean City in a storyline fight, and you can teach dig to Diglett (common) or Dugtrio (rare) in Diglett's cave, if they don't already have it.
Use dig when you're about to get hit by an attack that's charging. Also, use dig right before a Pokemon self-destructs, and it will always 100% miss while you're using dig. You'll get full experience points.