Instructions
Download the "GTA IV Magic Patcher" from gtagaming.com. Open up the download file and click "Run." This will run the program and install it to your system.
Download the "Dance and Taunt Mod" from the second reference link. This downloads as a zip file. Unzip the folder using an unzipping program and inspect the files. Drag the "GesturesMod.asi" file to your desktop.
Open your "GTA IV" gaming files and find the "gestures" folder. This should be located in the "Common" folder. Click on the folder to open it up.
Drag the "GesturesMod.asi" file from your desktop into the "gestures" folder. Without the "GTA IV Magic Patcher," you couldn't add new files to these directories.
Type "?" during gameplay to make Niko do one of four random dances. You can also press "G" to side, "," to make a random negative gesture and "." to make a random positive gesture.