My approach to voting is that you MUST vote for the candidate who best/nearly/almost completely meets your requirements; whatever they may be. No candidate is perfect, but one can comes really close to representing your belief, view and the needs of the country HAS TO GET YOUR VOTE. To not vote for such a candidate is wrong, IMO.
For Presidential elections, I believe one must vote for the candidate that represents the original view and interests of the country, as it was founded/framed. Accordingly, it has always been republican (REAL defense of the Republic) and constitutional. You may call that libertarian, if you wish.
Therefore, according to these requirements and through process, Ron Paul is the candidate, or Bill Still, if you are a Real Libertarian. Therefore, vote for either of these.
If you cannot vote for the candidate that comes really close to representing your belief, view and the needs of the country - DO NOT VOTE!
I talked recently with a guy at work (Michigan) who said he would vote for Ron Paul except for the fact (as he said) that RP can't win, and therefore my friend said he'd vote for someone who could win. I asked him if the second choice candidate met his needs, and he said 'no', but he wouldn't be 'throwing away his vote'. I then asked him just to vote for RP, and he said he just couldn't.
In his case, DON'T VOTE. Geesh.