In the nervous excitement of the day, it is important the last
minute duties are done. The ushers will usually be the first to
arrive at the ceremony venue and they should have several key tasks
and last minute checks to carry out.
The groom and best man arrive shortly afterwards; guests will have already started arriving. The bridal party should allow plenty of time to get to the ceremony venue. Meanwhile, everyone is waiting for the entrance of the bride.
See The Wedding Morning