Some customs want the bride unseen until the processional.  When indoors, the bride may be in a special room until the proper moment.  When outside, this may be more difficult to avoid mingling with guests before the ceremony.

For the bride who intends to really impress her guests, and many do, simply stay out of site until you make the glorious entrance.  This may include any bridesmaids as well!  Outdoors weddings: you can wait indoors, stay behind foliage, stay in the vehicle making sure to be picked up at the last minute.  In general, state what you wish, and we aim for fulfillment.