Do not vote for code length!
Code length is not a good way to determine what to vote for, because it isn't a good indicator of quality. A golflang submission can be thoroughly uninteresting and still beat out the most clever and well-golfed Python or Haskell submission out there.
Of course, golfing languages can have clever tricks as well (abusing the built-ins well is no easy task), and you should vote on them if they do, but don't do it merely because it's short.
By voting, you help to indicate that a submission is high quality. Quality is, of course, subjective—if it wasn't, Stack Exchange wouldn't need humans to vote. But many of the following things, to me, can make an answer good:
You can only be a good judge of the quality of a submission if you understand it.
Of course, what you vote for is up to you (short of voting fraud). Try not to let the existing votes on an answer influence your own.