2. Go to the S.S. Anne after you get HMCut:
After you get HMCut from the seasick old man, instead of walking out of the S.S. Anne, go battle another trainer. Make sure to lose this battle. You will appear back in Veridean Pokemon Center. If you go back, then the S.S. Anne will still be there.
I'm working on a followup to this glitch, where you surf in the S.S. Anne waters. I havn't beaten the 5th gym in my LeafGreen yet, but after I do that and aquire the ability to use Surf outside battles, I'll try it out.