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.
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.
Begin game play and reach mission 2. Get the baseball bat from the opponent that is on top of the fence. Next, jump off the fence and let the two thugs come after your character. Get the top thug to come to the end of the red pipes at the top of the screen. Once he is at that location, run up the fence and move all the way to the end of it. Then, turn around, jump back off the fence, and go to the end of the pipes. Although no opponents will be in sight, start swinging your bat at the end of the pipes for more experience and faster move learning.
Toward the end of Mission 1 (after you beat up the men with the barrel) you will reach a door and two girls with a jump rope. Keep walking to the right until you reach the wall, where there are two vertical bars. Press Up and you will walk up the wall. If you press A, B, or A + B, you will get hurt and fall off the wall. If you keep going up off the top edge of the screen, you will loop back and come up from the bottom.
Easy ability gain
On Mission 2 you can max out your statistics by climbing the fence, kill the Will at the top then drop down to the other side. Move forward and wait for Will to come close. When he reaches the end of the pipes in the background, climb back up the fence. Then move your character left until you walk to the edge of the yellow marker. Don't go too far left or the badguys will die and the trick won't work. (you'll now they died when the pointer tells you to go forward.) Then move back and Will should be invisible. He won't be able to attack, but you can attack him many times. If you have the bat, just hit the spot he was standing in over and over until you heart level is seven. You can keep hitting as many times as you want as long as the time doesn't run out.
Transform Linda's whip to a bat
On stage two, collect the whip from Linda before you climb the ladder. When you climb the second ladder, have the Linda knock down the player (the weapon is unequipped at the same time). Defeat the Lindas and pick up the weapon just before it disappears (pick it up on the second blink) and you will then have a bat to finish the stage.
Bypass Second Stage boss
At the end of mission 2, as soon as the end-boss comes out of the door, climb down the ladder. After descending a second or third story, you should hear the sound of victory. Your opponent has been defeated and you can move on to the third mission!
1st Level Glitch
Start playing the first level of Double Dragon until you see the second set of double doors. When you get there, take notice of the two vertical bars on the right hand wall. Kill all of the enemies, and then center Billy between the bars. From there, you can climb up and down without turning the characters back to you. If you go up, you can go off screen without losing a life. If you are up high, press left or right and you will "teleport" to ground level. Note: If you go too far down you will lose a life.