Of course, the first priority should be siblings. If the bride has a married sister, she could be the matron of honor. An unmarried sister would be the maid of honor. Additional sisters and friends would be bridesmaids. Or it you have a very special friend, she could be the maid or matron of honor. The tricky part is keeping your wedding party at a reasonable number.
The groom usually chooses a brother or best friend to be his best man. Additional friends are groomsmen and ushers. Groomsmen can also double as ushers.
Additional friends can be used as greeters and guest book attendants.
One thing to keep in mind–the more people in the bridal party, the more expense involved. If you are trying to conserve money, you might encourage your bride to limit her wedding party to her very best friends. However, realize that she probably has best friends from every stage of her life since elementary school.
To look symmetrical the number of bridesmaids should equal the number of groomsmen. So hopefully the bride and groom will have the same number of best friends!
There have been situations I’ve heard of where the bride has a male as an attendant and the groom has a female. I’ve never been to a wedding like this, but apparently is has been done. Maybe some of you have seen that.
One thing the couple might consider is coming up with a special way of asking friends to be a part of their big day. They might ask them over dinner or coffee or with a card that states why that friend is special to them.
And hopefully, those friends not asked will not be too upset!