The groomsmen at a wedding often serve as ushers to guests before walking with the procession and standing next to the best man during the ceremony. In many cases, the groomsmen host a pre-wedding bachelor party for the groom. The groom often chooses groomsmen from among his brothers or those of the bride-to-be.
As with bridesmaids, groomsmen pay for their own wedding attire. Unlike bridesmaids, however, they are often able to rent a tuxedo rather than buy their clothing.
In addition to hosting a bachelor party, groomsmen are obligated to attend all pre-nuptial events, including engagement parties, couple showers and the rehearsal dinner.
Groomsmen must be sure they understand the seating pattern at the wedding ceremony as they usually act as ushers. In most Christian ceremonies, the bride's guests sit on the left and the groom's guests sit on the right. It is usually the opposite in a Jewish wedding ceremony. Groomsmen should know the layout of the venue as guests are likely to ask various questions, such as the location of the restrooms.
Traditionally, groomsmen are paired with bridesmaids to walk down the aisle as part of the processional. Also, many groomsmen are asked to dance during the reception or wedding party with bridesmaids or female guests who attend without a date.