I believe that attitudes are the most important factor--once a libertarian attitude has been cultivated among the general population, it just takes a bit of organization to transform that into (some degree) of policy changes.

I believe that focusing on policy is worthless except as a way to generate interest in the libertarian attitude. Regular people have infinitesimal influence on policy--the only people with meaningful influence are political professionals (politicians, campaign workers, major columnists, etc) and the independently wealthy (that means that you don't have to work a real job, right).

Undermining the law depends on circumstances. Anytime we evade a law, we undermine that law--and this is a benefit-risk calculation for each individual. So for medical marijuana, it is probably worthwhile to evade the law (thereby undermining it). Also, I think that people are generally more capable of evading laws if they have more economic independence...and I think that is a worthwhile goal in itself. In the end, if a law is undermined by constant evasion, it is more likely to be repealed.

The main problem with the debate between lobbying for political reform and trying to create change through your lifestyle is the nature of the laws that you can work to oppose/change. Ending the War on Iraq is a big issue, aside from not entering the military how does one live their lifestyle in opposition to the war? But drinking unpasteurized milk? Well that's a more direct way of undermining the law. This means that the set of laws that can be undermined by personal action are smaller, more personal issues. Does that make them less important though?

So, if we're looking at voting based on big issues, what are some examples?

War & Peace specifically, with Foreign Policy generally, seem to be very important.

Domestic issues are more concentrated. I think it's easier to undermine the state by ignoring regulatory issues, like selling unpasteurized milk, than tax evasion. With social issues it's easy to ignore laws that may limit your free speech, but I also feel like political action to overturn those laws in the first place are important because they allow you to spread your message of subversion in other areas.

Undermining statist laws will normally just put each individual law-breaker at risk of jail. After all, millions "undermine" our marijuana laws, but that seems to make the Drug Warriors even more determined and fanatical. People are unlikely to break a law for the sake of principle, unless they were part of a movement in which tens of millions of others were mobilized to engage in the same act of civil disobedience. Undermining unjust laws requires a strategy; random acts, even if performed by lots of people, won't succeed. On the other hand, electoral politics hardly leads anywhere. If the last election didn't encourage the Democratic Congress to take a bold stand against the war, then what difference does it really make which party is in power?

That said, I in no way wish to discourage anyone engaged in undermining laws or partisan politics. But those aren't the only two options. Members of Congress do look at the polls. They are concerned about what their constituents think. They do sit up and take notice when they receive message after message from constituents expressing their views on a particular issue. (Special-interest money is most influential when people don't have a strong opinion on the issue.)

Contacting one's representatives, then, can go a long way toward policy change - if and when enough people get involved. No longer do people have to write addresses and stamp envelopes. Many activist organizations, such as the one I'm involved with, Downsize DC, provide easy and convenient means to contact one's representatives about an issue. It only takes a minute - maybe longer if one chooses to add their own thoughts to the message. Persistent and increased pressure on Congress can and will lead to changes in policy. This strategy has succeeded for groups that want to increase government, now we must use it to decrease government.