If you are a college student, like me, then you probably move around a lot. New year, new dorm room, new apartment, those kinds of things. Well, if your current address is not the address you had when you registered to vote, there is a good chance that you may have your registration disqualified.
As this post explains, a letter which is marked “Return to Sender” is enough to get you removed from the registration lists. So, a group or a company can send out mass mailings to registered voters and then simply go through the returned envelopes and disqualify those voters.
This causes all kinds of problems for people who move often, including college students and those in the military, especially those who are serving overseas. As outlined in the post above, this has had some pretty major effects in past elections and primaries. Can you imagine serving in the US military and not having your vote count? That sucks.
Anyways, if you have moved recently (like I did), be sure to re-register to vote. If you are in California, this is super easy. You can go here and request a registration card. They will send you a card in the mail with all your information filled out. All you have to do is sign and return it. I suspect other states have similar websites.
Also, if you are super lazy (again, like me), you may want to permanently register for vote-by-mail or absentee ballots. This means you don’t have to remember to go to the polls or miss school/work/sleep to do so. You’ll get a ballot in the mail and you just have to send it in soon enough to beat the closing of the polls. If you are forgetful, though, you can also take the mail-in ballot to a polling location and turn it in there (yes, I know this from experience).
If you are planning on voting (and you probably should), then I would really recommend doing the above.