My answer would be that you shouldn't, and I must say both as the one who asks, as well as the author of the accepted answer, I'd consider it a kind of a contempt. 

while anyone has the right to vote for (or against) the quality of an answer, it is the exclusive privilege of the one who asks to *accept whichever answer he or she considers most useful*. OP does not need to defend his choice, nor should anyone use any pressure to accept this or that. I have seen it in the passed more than once, and found it horrible without exception, Not to mention that I often disagreed with the claimed "*this is the best answer*".

Really good answers will often attract more votes over time, accepted or not. The gloomy attempt to push someone simply isn't serving any goal.