RijonAdventures - How to get Strength, Waterfall and how to get into the Warehouse near Botan City.
To get Strength: Defeat the 7th Gym to get the Psi Badge. Go to Merson City and talk to the old guy blocking the spas. He'll now let you through. Go into the spas and search for the Go Goggles (also get Rock Smash while you're here by talking to the old lady/man). Now go to Eagulou City and enter Eagulou Park (the Safari Zone style place). Head to the left and go up. You should enter a cave. Work your way around the cave (it's not that hard) until you end up outside in a sandstorm. As you have the Go Goggles you can continue walking. There will be a item on the ground that you need to pick up. It's a camera, although its doesn't state it in its name. I can't remember its name, but it starts with "E". Anyway, you pick this up and go to Hayward City. Head to the left, go past the Department Store and then Surf across the water and enter the house. Talk to the guy and he'll give you Strength for getting his camera for him.
To get Waterfall: Go to Castro Valley and then head north. Use surf on the lake to the left and enter the cave. Use Rock Smash on your way down and go through the "entrance". Head left and go through the next "entrance". From here you'll see 3 Stength-movable rocks, accompanied by 3 Rock Smash-able stones. Break the middle stone with Rock Smash and then use strength to push the rock all the way through. Head north through another "entrance" and you'll be in an icy cave. Head north into another entrance. You'll now be in a room with a ladder 3 steps to the north and icy paths to the right.
You'll soon work out that the ice will crack if you walk on a certain tile more than once, or if you walk on a cracked tile. For the first one go right, down, right, right, up right. Second: up, left, (note: you can walk on the stone currently to your left and if you walk onto the stone and then back onto the ice tile you were previously standing on you will fall through and land on a stone lol) up, left. Now go north and up the ladder. Now drop down the ice tile in the middle by stepping on it twice. You can get the item to your right after getting through the ice maze. (answer: right, up, left, up, right, down, right, down, right, down, right, down.) Drop down to the next level by jumping over the ledge. Head south to the next ice maze. (Answer: right, down, right, up, left, down) Now go up the ladder and the waterfall HM will be at your feet. Now drop down the next few levels and you'll be back at the start.
Getting into the Warehouse: Go to Botan City, head south from the mart and use surf on the right hand side of the bridge. Follow the river around and enter the building. (I'm not sure if there are any other requirements before you can get in here, other than having Waterfall.) The guy will tell you to go help his daughter in the Haunted Woods. So head back to the Haunted Woods and the lady will now let you pass. Surf on the water and use waterfall. Head right and use Cut on the tree. Continue to head right then head north. You'll fight a few Rockets. After defeating them, head north, then left until you reach another tree that you can Cut. Cut the tree and then head south. Use surf on the water and then continue south until you reach the bottom. From here go right and talk to the girl. Now you'll fight a lvl 50 Gengar. You'll then be teleported back to the building.
Red will come and ask you to go with him to Goldenrod City, which can be reached through Cycling Road. But first, you'll need to get the Pokeflute, so you can wake the sleeping Snorlax at the end. Head back to the Pokemart in Botan City. From there go right and then north and you'll see a tree that can be Cut behind the house. Cut it and walk north through the fences and talk to the girl at the top right (you'll only be able to see her reflection in the water). She'll give you the flute. Now go to Cycling Road, which is to the west of Owsuari City.
After working your way through cycling road and defeating, or capturing, the Snorlax. You'll eventuall reach a house where you can go either north or south. Go north to Goldenrod City. Enter the building with the orange roof and talk to Tim and Red to the right. Now you'll be able to go into the Warehouse.