Apushatay, not much is expected of you. Semi-discreetly pass the badchan a few $$ and say something friendly to him. Try semi (or not) discreetly to notice how much your brothers (in-law) or others give him. Take the gartel, or sometimes they have a long piece of fabric with kol sasson etc embroidered on it. This will be passed to you by a cute little boy from the family, the badchan, or other guy who got the job. Try to find the perfect balance between looking directly at the kallah and giving her a big goofy grin (Not good) and looking away, ignoring her, and staring at the ceiling (also not good, unless you are an extremely important Rabbi. Do a liitle tantz, sway back and forth a little and move your feet. No major complicated dance steps expected. Since the chosson is your nephew feel free to approach him before the ordeal and ask him to rescue you as quickly as he can. If not possible you can also ask the chosson’s father for the same favor. They”ll walk over, take the gartel away from you and then you get to dance with the chosson, his father and the whole mishpuche.
Menu