You're the best man—now what? Of course, there's planning the bachelor party and delivering an epic best-man speech. But that's just the beginning. In a nutshell, the best-man's role is to do everything possible to take weight off the groom's shoulders, which will likely include any (or all) of the following duties.
BEFORE THE WEDDING
Provide emotional support and be a sounding board as he shops for an engagement ring, as well as throughout the wedding-planning process.
Help the groom decide on what he and the other groomsmen should wear; coordinate any groomsmen attire rentals, if necessary.
Coordinate travel and accommodations among the groomsmen. If it makes sense for the group, you could help pair up groomsmen to share hotel rooms or rental cars to save on costs.
Organize the bachelor party (but enlist the rest of the groomsmen to help, too).
Coordinate the groomsmen's gift to the groom.
Attend pre-wedding events like the engagement party, rehearsal, and rehearsal dinner.
ON THE WEDDING DAY
Get dressed with the grooms and groomsmen; keep a close eye on the clock to ensure everyone is on schedule.
Get any outstanding vendor payments from the groom (for the wedding officiant, musicians, etc.).
Make sure the groom and groomsmen arrive to the ceremony venue on time and fully dressed.
Make sure everyone is wearing their boutonnieres, if using.
Hold on to the wedding rings until the couple’s ring exchange.
Greet wedding guests as they arrive to the ceremony.
Line everyone up in correct processional order before the ceremony begins (according to what was practiced during the rehearsal).
Make sure the ring bearer is ready and knows what to do.
Stand next to the groom during the ceremony.
Escort the maid of honor up the aisle during the recessional.
Deliver payment to the officiant and any other vendors, if this has not been done already.
Serve as a witness during the marriage-license signing.
Drive the newlyweds the reception venue, if needed.
Pose for wedding photos throughout the day as needed; help wrangle any missing family members or friends for various group photos.
Be announced with the maid of honor during the reception entrance.
Play the role of host—mingle with guests and help answer any questions.
Dance with the maid of honor once guests are welcomed onto the dance floor; also make sure to dance with the bride.
Check in on the groom and make sure he's gotten a chance to eat and drink.
Give the best man speech (his biggest responsibility!).
Decorate the getaway car (enlist help from other groomsmen and bridesmaids).
AFTER THE WEDDING
Take care of the groom's clothes after he changes out of his wedding attire, if the couple is leaving directly from the reception.
Collect any cards and gifts from guests to hold until the couple’s return.
Hand out tips to vendors, if the couple has asked you to do so.