Points recognize people's initiative to stick their neck out and take a stand. The more often you participate in your blocs, the more likely you are to accrue points:
After you endorse a vox, you gain a point every time someone else endorses that vox.
After you deny a vox, you gain a point every time someone else denies that vox.
After you propose a vox,
you gain a point whenever it is endorsed, and
you lose a point whenever it is denied.
Since points are rewarded when others follow your vote, it helps to persuade others to do so—argue your vote in the comments, or share the vox and encourage others elsewhere on the web.
Point totals can be seen in a bloc's member listing (click "Show" at the top-left of a bloc page), on an individual's Profile Page (in their bloc listing on the right), and when hovering the mouse over a person's name throughout the site.
The fine print:
Points are specific to a bloc, so having a high point total in one bloc doesn't reflect one's initiative in another bloc. This also means it doesn't make sense to compare points across blocs, and that the High Scores page is just for fun and shouldn't be taken too seriously.
Leaving a bloc doesn't affect your ability to receive or lose points. Points will continue to be tallied for you in that bloc based on your previous actions. If you ever re-join the bloc, your points will reflect that ongoing tally.
If you change your vote on a vox, you forfeit any points you earned from others who voted likewise after you. For example, if you were the first of five that endorsed a particular vox, you would have gained four points. If you later decide to deny that vox, you will lose those four points and start over gaining points in that vox.