At a church wedding, the ushers often will ask guests, "Bride's side or groom's side?" But which side is which? And why?
Wedding lore tells us that hundreds of years ago, kidnappers often absconded with the bride in order to steal her dowry. So, in order that the groom might keep his sword arm free, the bride stood on the other side - the left. Today, in spite of the fact that the groom rarely wears a sword, nor needs to fend off attackers, you'll almost always see the bride standing on the groom's left. It's also traditional for wedding guests to follow suit - the bride's guests and family sit on the left, while the groom's family and guests sit on the right.
Of course, unless your church is strict about tradition, there's no reason you can't switch things up. You might have more mutual friends than you do separate friends, or, in a same-sex wedding, such questions might not apply. But even if they do, feel free to designate either side as your own.