Organizing the Receiving Line:
My parents are divorced, and both have remarried. How should everyone stand in the receiving line?
Divorced parents do not normally stand in a receiving line together. That honor typically goes to the parent who hosts the reception (and the stepparent, if there is one). When divorced parents are friendly and accept each other's new spouses, or when both sets of parents are hosting the wedding, they may all stand in the receiving line, separated by the groom's parents to avoid any confusion. If the groom's parents are divorced and remarried as well, then the bride's sets of parents should alternate with the groom's so no one is standing next to his or her ex. Of course, what's most important isn't where everyone stands but how they feel about it. In order to head off misunderstandings, it's best to talk with all parties early on about what your expectations are.
My mom and stepmom are not on great terms, How do I handle seating at the wedding, reception, and other events?
It's prudent to think about this before the rehearsal so that you can give divorced parents specific seating instructions in advance. Traditionally the bride's mother and her husband sit in the front row (if the bride is much closer to her father, he and his wife may sit there). Members of the mother's immediate family sit behind her, in the next one or two rows. After escorting the bride down the aisle, her father should sit with his wife in the next row back. If you plan ahead for the reception, you can make it easy for your mom and stepmother to avoid interacting. Assigning them to tables at opposite ends of the room is a good start.
Walking down the Aisle:
I would like my stepfather - not my father - to walk me down the aisle, as he has played a more active role in my life (he's also paying for the wedding). But how do I tell this to my biological father? The aisle is not wide enough for them both to escort me, and I'm beginning to think I'll have to go alone just to spare everyone's feelings!
Walking down the aisle by yourself isn't your only option (though some women prefer this to being given away). One choice is to have your mother accompany you; this would work well if you two are especially close. Or you could include both fathers: Ask your biological dad to take you halfway, then meet your stepfather and walk with him to the altar. The other solution is to have your stepfather go with you the entire way. After all, you say he has been more involved in your life, and so he certainly should have a major role in your wedding. Have a heart-to-heart with your biological dad and gently tell him your plan. Assure him that you love him (surely you do) and have other meaningful ways to honor him. See if he'd like to participate in the first father-daughter dance, do a reading or light a unity candle during the ceremony. If you're sensitive to both fathers' feelings and express your wishes honestly and tactfully, you'll find the solution that's best for all.