Warps
Warping allows Duke to essentially teleport around the map. You may be familiar with warp zones. These are intentional warps placed by the map designer. The types of warps I will speak of are unintentional products of the game engine and map design. Typically, you have to move your body in a certain motion at specific areas of a map in order to activate these unintentional warps.
Type 1 - The most basic type of warp allows you to warp through certain walls down to the ground by simply running into the wall. Typically, a door will exist at the bottom and you warp from the wall down through the door. It's as if you went through the door in an instant. A good example of this warp takes place in Hollywood by the double doors inside the theatre. Position yourself anywhere above the double doors (even at the very top of the theatre) and simply run or fly through the wall while opening or closing the doors. You will instantly appear outside the doors.
Type 2 - The second type of warp typically involves strafing + ducking slightly on a thin path. A good example is in Hollywood in the red window outside. Jump, then strafe + duck ever-so-slightly onto the ledge of the window furthest from the red sign, and you will end up in the arcade.
Type 3 - The third type of warp involves a technique I call "strafe-ducking" or "strafe-jumping." The basic idea is that, at certain areas, you can use strafe-running + duck and warp to other places. There are so many examples of this. For instance, some doors let you strafe out of them using this. The jetpack warp in Hollywood uses this technique. Areas where the ground has a hole or crack that is too small will let you through using this technique. Also, you can use it to warp to the bottom or top of rotating-type objects like gears. To make this more effective, some players also press jump immediately when they land on the surface of the area to warp. This will be the most useful warp to you.
Type 4 - The fourth type of warp is a variation of type 3. Sometimes, it may seem like you can warp at a place, yet it doesn't appear to be working. This may be because you have to land more precisely. A great example is the ledge at the bottom of the two atomics in L.A. Rumble. You can use warp type 3 to warp into the right corner up to the atomics, but you have to do it slightly, so as to barely land on the ledge without much forward momentum.
Type 5 - The fifth type of warp allows to you be crushed by objects, mainly doors, and appear elsewhere. For instance, you can use this behind the outside doors of the theatre in Hollywood (1.3D version) to warp to the area near the box. You simply crush yourself by strafing into the door hinge and opening the door.
Miscellaneous - There are some miscellaneous, lesser known warp types, some only working in 1.3D. They may fit into categories above, but I decided to break them out. The first is called the crack warp. This is simply strafe-running into a crack and jumping right when you reach it. The best example of this is the cracked wall near the steroids in L.A. Rumble. The next type is what I like to call the hinge warp. This involves opening a door from the side opposite of the door's opening direction. Then, while strafing into the hinge, close the door. The only example I recall of this is on the doors outside the theatre in Hollywood. You end up arriving at the jetpack (1.5 version). The next type is called the rolling door warp. In this warp, you mess up a door's natural rhythm, causing the door to slide upwards into the wall more than usual. Then, you close the door and strafe-jump into it as it's closing. Again, the only example I recall of this is by the elevator in Hollywood. There is a door with night vision in it that allows you to warp into the projector room. Another warp type is called the jittery warp. This involves slowly crushing Duke and then warping as he starts to shake. One example in Hollywood is the broken out wall near the doors to the projector room. You can jetpack in it and as you start shuttering, you warp into the projector room soon after. Lastly, you may have gone up against a window or door and started to shake a lot when strafe-running into it while ducking. Upon jumping, you bug. Sometimes, these warps require steroids to get enough speed to get through. But, it is possible you can get through using a pipe bomb. What you do is place the pipe bomb a bit back from the object. Then, as you jump towards the object to warp, detonate the pipe bomb. If all goes well, you will get the extra explosive boost you need to warp through. You can even add steroids for greater effect.
So, as you can see, there are many types of warps. The miscellaneous warps are novelty warps, largely removed from the 1.5 version of the game. If you have to learn one type, learn type 3. You will start realizing where warps would be possible in user maps just by practicing this warp type. Then, you can find more in obscure maps! Click here to see demos illustrating some of these warps.
Falling
What goes through one's mind as they fall hopelessly to their death in Duke? Probably something along the lines of "Why won't my jetpack activate!?" Well, unbeknownst to some dukers, there are ways to survive falls without a jetpack.
Type 1 - The simplest way to avoid death from a long fall is to use trip mines and stick them to nearby walls. In this way, you will slow your fall rate and be able to land normally or with minimal damage.
Type 2 - The next way to avoid death from a long fall requires the shrinker. Basically, you can fall while shrunk and not incur any damage if you land before you become unshrunk. However, this is used more as a way to get to the bottom of the map when there are no lasers, or when you know there is some item like the jetpack at the bottom.
Type 3 - This final way to avoid death from a long fall is the hardest, but most widely applicable. Essentially, objects like trash cans, boxes, and signs can be landed on without dying. Ledges and bridges can also be landed on. Also, windows can be landed in. There are two main ways to do this. The first way is to slightly clip the very edge of these items. Duke will simply hit it once then fall off and take no damage. The second way is what I call a soft landing. Duke will land completely on the object, yet incur no damage. It will be as if the object is a pillow. The method to doing this is still not 100% in my mind. One way is to simply turn slowly as you are about to fall on the object. This appears to increase your likelihood of not dying. Another way is to gradually move towards the object right before you land. Again, these aren't 100% ways, but they work a lot in my testing. Also, to land cleanly on solid ground, it appears that it needs to be sloped a bit.
So, as you can see, a long fall may not be so bad afterall. Click here to see demos illustrating some of these falls.
Miscellaneous
Here are some glitches that don't quite fit into any category. While these may not help you in competition, they're fun to try.
Glitch 1 - Have blue press F7 in deathmatch. Then, have blue restart the map. Red is now invisible! You can still shoot red, and you will see the blood, but you won't see the player!
Glitch 2 - Shrink one of the non-dukers (like a hooker). Next, shoot her while small with the freezer. When she re-grows, she will be indestructible.
Glitch 3 (DOS 1.3D only!) - Right when you're about to put a laser on a wall, jerk the mouse to face another wall. Duke will throw the laser on that latter wall instead! You can use this to throw lasers onto walls far away.
Glitch 4 - A good way to toss pipe bombs in the air is to duck and mouse aim far down facing the ground. Try shooting some with your shotty afterwards! Another way is to just aim up without ducking.
Glitch 5 (DOS 1.3D only!) - Have Duke go up against a wall or door and press F7. Then, press escape. The longer you leave it on the menu, the further it will zoom once you press escape again. You can see through walls! For example, you could see someone in the projector room from the red room outside in holly.
Glitch 6 - If you kill someone and it left behind a body, you can tell if they respawned by watching their body. If they are still dead, their body will glow under night vision. When they respawn, their body will stop glowing. Their body will also disappear after respawning in 1.5.
Glitch 7 - You can tell a player from a holoduke by noting that a holoduke doesn't glow under night vision, but a player does. Also, you can tell by shooting, haha.
Glitch 8 - Many sector types allow you to throw pipe bombs through the wall. Some walls, all it takes is to be face first right up against the wall and throw the pipe bomb normally. Others, you should position yourself along the wall and throw the pipe bomb at a slight angle into the wall. Some of these latter ones only work on 1.3D.
Glitch 9 - If you have one or more pipe bombs laying somewhere and you are killed, you can still detonate them after you respawn!
Glitch 10 - If you are full on pipe bombs, you can toss one of them, go grab a box, and it will boost you back up to full, but the box will still be there!
Glitch 11 - Get above 100 health with some medkit and armor. Rocket yourself into a wall while activating medkit quickly. You may end up using some medkit, yet being above 100 health still!
Glitch 12 - You can hide inside mirrors by duck (release) strafe-running into them at an angle (or being on steroids and backing into them, but this is less ideal). When in the mirror, you can't be seen, except for your shadow, which is still hard to see at times. You can use this to hide from foes and launch surprise attacks. But, beware, as someone can still RPG the hell out of you or jump inside the mirror with you and shoot you with other weapons!
More Info
For a more technical explanation of warps and other glitches, go to Red Stars. Also, you may be interested in these old DOS 1.3D demos from Bug Team. Click here to see those.