To use these, simply create a shortcut to Exoddus.exe in the games install directory, right click the shortcut and select properties. Append the argument after the closed quotation with a space like so:
Alternatively, go into the game's properties from within your Steam library, click "set launch options" and add the argument there.

Arguments:
-ddcheat
This puts the game into a sort of debug mode that allows you to fly around the levels. Press the tab key when in game to activate debug mode, use the arrow keys to move abe around. shift+ arrow keys to move faster. Pressing tab again will drop abe back into regular mode.

-ddfastest
This mode was the main impetus for throwing together this little guide. This makes the game display in an interleave video mode that skips lines in the display for a scanline effect. This was originally intended for computers that were slower than the recommended requirements but some people may prefer how it looks. Depending on how you have screen scaling setup this makes the game look much better, it hides how poorly some of the environments were scaled. It does make the game look darker but that I think that suits the game just fine. If you have an nvidia card, make sure you have scaling set to aspect and that scaling is performed on the GPU in the driver settings. The scanline effect should appear nice and even if you have it set correctly.

-ddfast
Runs the game in a lower resolution. Again intended for slower computers. Because of the aspect ratio of the pixels this looks pretty messy and ugly. I recommend -ddfastest over this mode if for some reason you are running on a potato and need to speed up the game.

-ddnoskip
Removes frame skipping and also frame rate cap. I believe this was intended for slower computers where the game would skip frames if it was running too slowly, making the game appear choppy but running at the intended speed. This would disable that behaviour and instead run the game at a slower speed without skipping over frames. On modern computers this has the effect of running the game in fast forward.

-ddfps
Displays a frames per second read out in the top left corner.

-syncread
Not sure what this does, I'm assuming it changes how it syncs frames but I can't tell what effect this really has.

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If you installed this game from disc back in the day you may remember it creating shortcuts to faster video modes in the start menu. These were just shortcuts with the -ddfast or -ddfastest arguments enabled.

If you want to use more than one argument at a time simply separate them with a comma. Eg:
-ddnoskip, -ddfps