The Knot lists several tasks for the best man, including being in charge of outfitting the groomsmen, planning and throwing the bachelor party and giving the first toast at the after-wedding party. There are additional duties related to these main tasks that might be asked of him depending on the groom's preferences.
Getting the groomsmen outfitted requires ensuring the other groomsmen attend fittings and making certain they arrive with the correct attire at the wedding along with all the necessary accessories, such as shoes and ties. The best man helps the groom dress on the day of the wedding. Packing the groom's clothes for the honeymoon is also sometimes expected.
Planning the bachelor party includes finding a location, inviting guests, arranging for food and entertainment and collecting money from the guests to cover the costs. The best man's work at the wedding includes transporting the ring to the ceremony, escorting the maid or matron of honor down the aisle, signing the marriage license as a witness, dancing with the bride and giving the first toast at the after-party. He also typically arranges for transportation after the party and works with others to decorate the bride and groom's car if they are driving away themselves.