Chargestone Cave 1F
Follow along the path until you reach Bianca examining a glowing crystal. After talking with you she'll simply walk off. Go in the direction that she left in. You'll eventually reach a large crystal blocking your path. Move to its right side and push it into the huge crystal east of you.
Now go through the gap that was created, then around the huge crystal to grab the Full Heal below it. Move back around the huge crystal and continue on north. You'll reach another large crystal. Push it towards the huge crystal to its east to open up the next area.
Head through the opening then move up the eastern set of steps to start a battle with a Scientist.
Trainer Battle: Scientist
Move south from the Scientist and push the north-eastern of the two crystals east, into the huge crystal. This will create an opening which you can walk through. Do so and grab the Max Repel that was hiding behind them. Backtrack down the stairs, then take the the northern set of steps to initiate a battle with a snazzy Guitarist.
Trainer Battle: Guitarist
Turn on your Dowsing MCHN. There's an item hidden above the ridge to the Guitarist's north. Go east then around onto the ridge above. You'll find the hidden Yellow Shard underneath the floating crystal. Go east again then continue along, past the two crystals blocking the past south.
You'll see a Hyper Potion to your north-east. Go over and grab it then move back to the two crystals. Push the top one west, and the bottom one south. Follow it south, then continue down the steps. Head east to the huge crystal there.
If you go south, you'll come upon Bianca talking with a Worker, who are blocking your path. Apparently you can't go any further just yet. Instead, take the stairs north. Once you've ran up them, make sure your Dowsing MCHN's on then move east, then south and grab the hidden Hyper Potion .
And that's all you can do here until you've beaten Clay at the Driftveil City Gym! It's about time we headed there, don't you think?
However if you've already completed the Plasma Frigate (via PWT) section, skip straight to Chargestone Cave Part 2 and continue on through the rest of Chargestone Cave!