There are 9 warp portals in A Link To The Past which will take you from the Light World into the Dark World. This is handy to know when playing the game.
1. The first warp portal you come across is in the middle of death mountain, you need to use this to get to the Tower of Hera.
2. The second warp portal is north of Kakariko Village. You can get to it by going into the lost woods and then back out again at another entrance or by lifting the heavy boulder.
3. The third warp portal is located at the Entrance to Hyrule Castle. This only becomes a portal after beating Agahnim.
4. The fourth portal is just south and left from links house. There is a couple of stakes. Hammer them and then lift up the rock to reveal another portal.
5. The fifth portal is at the entrance of the Pond of Happiness. There is a rock in front so lift it to unviel the warp portal. You use this one to enter the Ice Palace.
6. The sixth portal is south of the Eastarn Palace. There is a square of stakes. Hammer away into the middle and lift the rock to go through the warp portal.
7. The seventh portal is at south-west of the Desert. You have to use the flute to get there.There is a small rock covering the portal, lift it to reveal it.
8. The eigth portal is on Death Mountain. To access it, cross the Broken Bridge, head downwards, and there is a small rock. Lift it and there is the warp.
9. The ninth portal is on top of Turtle Rock in the Light World. To make it appear, hammer the right stake followed by the top stake and finally the left stake. This warp is necessary to get into Turtle Rock.