In days of yore, the best man was the one who helped the groom kidnap the bride.
When her family set out to rescue her, he would stand and fight so the groom could make a clean get away.
Over time, the position has evolved to the point where it's not always a man standing up there at the groom's behest.
Before you ask anybody to do you the honor, you need to consider a few things.
The person who matches the expectations may not be your best friend.
He may be too busy or just plain too absentminded to fulfill this very serious, complex role.
Ask yourself a few questions to get your answer.

1. For whatever reason, is there somebody you want to put in a place of honor on your wedding day? Say, for instance, your sister.
   If there's not a doubt in your mind that she'd be your best man if she'd been born a boy, then there's no reason she shouldn't take the position.
   She will have to discuss with the bride whether she'll be wearing a tux as well, or matching the bridesmaids in a more feminine fashion.
   
2. Is your best friend female? Same sentiment applies.
   Why should somebody, who is not as tight with you as she is, get to stand by your side on the most important day of your life?
3. Do you have no close friends? Some of us are loners.
   If your future wife has somebody that matters a great deal to her, why not let him do the honors? Of course, the best man has a great many responsibilities and obligations, so I'd at least want to know that much about them.
   

Traditional weddings are going by the wayside.
Unless you are marrying a traditionalist, there's no reason for you to do things the old-fashioned way.
Having said that, you can extrapolate it out however you wish.
So what if your best friend is absentminded? You can use technology to keep him on the straight and narrow.
If you fear he's going to misplace the rings, don't hand them over.
Just make a decision: Do you want your best friend standing as your best man on your wedding day? If the answer is yes, then you do whatever you have to do to help him complete his duties.
A couple of years ago, a groom in the UK chose his Springer spaniel to fulfill the role of best man.
His rationale was he had more than one best friend, and he didn't want to hurt anybody's feelings.
They brought Frank to the church, and got his presence approved by the minister.
Frank had a wonderful day.
The minister even put out a water bowl for him.
He wore a hat and tuxedo collar for the festivities.
And at the reception, he didn't hump any more legs than the average best man.
All in all, Frank was a hit.
May you be so blessed with your selection for best man.