A lot of these "superstitions" originated in other cultures for reasons having nothing to do with good or bad fortune.
"Seeing a bride before the wedding"  ?  Well, in countries and cultures where marriages were arranged, the bride and groom
 may not meet before the wedding.  White dresses have nothing to do with purity and everything to do with proving your family is wealthy enough to buy you a dress that's only used one time.  
During the "marriage by   capture" era, close friends of the groom-to-be assisted him when he kidnapped   the bride from her family. The first ushers and best men were more like a small   army, fighting off the brides angry relatives as the groom rode away with   her.
 

Bridesmaids and maids of honor became more common when weddings   were planned. For several days before the marriage, a senior maid attended to   the bride-to-be. This maid or matron of honor, as we know her today, ensured   that the bridal wreath was made and helped the bride get dressed. All   bridesmaids helped the bride decorate for the wedding feast.
 
For a long time, bridesmaids wore dresses much like the bride's   gown, while ushers dressed in clothing that was similar to the groom's attire.   This tradition began for protection against evil rather than for uniformity; if   evil spirits or jealous suitors attempted to harm the newlyweds, they would be   confused as to which two people were the bride and groom.
 
The wedding is one of life's   primeval and surprisingly unchanged rites of passage. Nearly all of the customs   we observe today are merely echoes of the past. Everything from the veil, rice,   flowers, and old shoes, to the bridesmaids and processionals, at one time, bore   a very specific and vitally significant meaning. Today, although the original   substance is often lost, we incorporate old world customs into our weddings   because they are traditional and ritualistic.
Old world marriage customs continue to thrive today, in diluted,   disguised and often upgraded forms. Customs we memorialize today were once   "brand new" ideas. Although historical accuracy is hard to achieve, the   historical weight attached to old world wedding customs and traditions is   immense. While reading through these pages, feel free to use, reinterpret, or   omit them in your own wedding.
Remember, as you plan for your wedding, to create new family   traditions and customs to be handed down to your children and their children.   Just think, maybe someday, your "new custom" will be as unique and exciting as   these presented here.
 
All wedding and engagement rings are worn   on the fourth finger of the left hand. The vein in this finger was once believed by ancient Romans to go directly to the heart. Pretty obvious symbolism   there.