This tip requires two gameboys-One with pok'emon Crystal and the other with pok'emon Blue,Red,or Yellow-If any of you haven't noticed Pok'emon Crystal doesn't have the HM dig anywhere but it had this HM in the older pok'emons.To get this HM back,you are going to need to get the HM in one of the older pok'emon games and then teach it to one of the older pok'emon.After doing this you are going to need to trade it to the newer Pok'emon Crystal version.(This HM is really handy in hard caves that you can't get out of and if you're out of escape ropes. It also helps in battles because the enemy automatically misses once,stopping moves like rollout etc. from getting stronger)