Double Dragon Cheats
Accumulate 1000 experience points, as noted in the counter the bottom left corner. One additional heart and a new move (in the following order) will be awarded: Uppercut, Jump kick, Hair pull, Pin attack, Elbow punch, Spin kick.
Defeating Chin easily
The level two Boss, Chin, can be defeated by quickly climbing down the ladders after he appears. Keep climbing downward until the end of level music is played.
With this trick you can get all of the hearts in Mission two! First, get to the second round and play until you reach the Williams with the baseball bat on top of the ledge. After you defeat the Williams, walk slowly to the right until you are facing a pile of red girders. YOU MUST BE AT THE VERY TOP OF THE SCREEN AGAINST THE GIRDERS! A Williams will come out at the right of the screen to get you. While he is approaching you, walk back to the left towards the wire fence. When Williams is right in front of the left edge of the girders, begin climbing up the wire fence. As you climb, Williams will stay where he is standing. Climb to the top of the fence and walk on the ledge, going left. Climb down the first wire fence on the left and go as far to the left as you can go. Once your man cannot go any further, go all the way back to where you left the Williams standing. If you keep hitting the exact spot where Williams was standing (he won't be there now), you will keep getting points. Keep hitting and get all you hearts!