Once you've conquered the Elite Four, you'll wind up back in Newbark Town. Go to Professor Elm's lab and speak with him. He will give you an SS Ticket for the SS Aqua, which is stationed in Olivine City. Before flying away, speak with your mother if you're low on funds. You shouldn't be since you just beat the Elite Four, but you never know.

From the Pokemon, go south and enter the building. Follow the path and you'll wind up at the docks. Speak with the sailor and he'll let you on.

Once inside, you'll be asked to find a man's granddaughter. On the right side of this floor is a staircase that leads to the bowels of the ship. Go down there and a sailor will stop you. Go find his mate on the previous floor and battle him, then you can proceed.

Once you beat the sailor's mate, you can continue on. On the other side of the lower deck is another stair that leads to the captain's room. Speak with the little girl, and she will return you to her grandfather where you will be rewarded with a Metal Coat, an item that evolves Scyther or Onix. The ship is in Vermilion City at this point, so exit the ship.

Leave the dock area and the hut that connects the docks to the city. Explore around the city for the Pokemart and the Pokemon Center. Heal your Pokemon and buy any items you may needs.

The gym is in the lowerleft part of town, and you'll need Cut or Surf to reach it.

In RBY you had to find the hidden switches inside the trash cans. This is no longer the case. You can just walk back to where the gym leader is.

All his Pokemon are weak to Ground-type moves. If you picked up TM26 back in Victory Road, teach it to a good Pokemon and spam the hell of it.

Alternatively, use Fire-type moves on Magneton.

Lt. Surge, unlike the Johto Gym leaders, will not give you a TM. Cheapass.

Anyway, return to the Pokemon center and heal your Pokemon. Time to head north into Saffron City. Can't go east because Snorlax is blocking the road.

Keep going up from Vermilion into Route 6 and you'll hit Saffron City.

Few things to do here. One, visit Mr.Psychic's house. Go to the right as you enter town and it's the one with a sign in front. He will give you TM29, which is Psychic.

Head north from his house and you'll find two gyms. The gym on the left houses the Focus Band item. The one on the right is the gym for Saffron. Best to bring along some Dark-type Pokemon.

The easiest way to get to Sabrina (after stepping on the first warp tile) is to go to the tile directly to the left or right each time you warp. When you want to return to town, just repeat the process. After a few warps, you'll find Sabrina.

The good thing about Psychic Pokemon is that they have terrible defense. So if you lack a Dark-type Pokemon or a Dark-type move, it would be best to bring along some heavy hitters, particulary those who know Body Slam and Slash. Earthquake would be good as well.

Just spam those Normal-type and Dark-type moves and use restorative items when you need to.

After you beat Sabrina, return to Saffron and continue north into Route 7, then into Cerulean City.