This being election day, you're seeing a lot of people telling you to get out and vote, saying that if you think your vote doesn't count you're abdicating democracy, reminding you how many people who died so that you could vote, etc.
I have to admit I find these exhortations both facile and manipulative. If we're talking about the presidential election, sure, you can make an argument that "every vote counts". That argument is not really practical, however, because of the electoral college. Every vote for president counts only in a small number of battleground states. I used to live in California; everybody knows that California is going to go to Obama. The Obama and Romney campaigns certainly know it; how much time and effort did they spend trying to sway California voters? Now, strictly speaking, if everybody who would vote for Obama figured it didn't matter and as a result didn't vote, then, yes, Romney could pull out a surprise win. But, while that's a theoretical possibility, let's be realistic here about how likely that is. It's not going to happen. As a result, if you tell somebody in California that their vote for the president really matters, you come across looking either naive, or manipulative.
So should you vote anyway? Yes. Two reasons.
First, to stay in practice. The USA's current system of elections is horribly corrupt. Jimmy Carter has spent a lot of time overseeing elections in other countries, and he says that about our elections. Also, check out rootstrikers.org, a website related to Lawrence Lessig's book Republic Lost. It's easy to become cynical, to realize that everybody running for any office is dancing to the tune of large campaign donors, and to give up and not bother voting. However, you must vote, both because there are differences between candidates, and because you need to stay in practice, and we need to keep voting as "a thing" that we do in the USA, in hopes that we do manage to fix the corrupt system.
The second reason is: there are elections other than president. If you live in California, no, it doesn't matter who you vote for for president; Obama's going to get your electoral college votes, whether you like it or not. However, there are congressional districts whose representatives are not a foregone conclusion. And, in many states, the Senate seats may well not be a foregone conclusion. Congress matters. You need to vote there. Additionally, there are going to be state and local elections that matter. You need to vote there. With all of these other things, there isn't an electoral college making your votes irrelevant; in these other races, every vote does matter.
So, yes, get out and vote. But, please, let's stop pretending that every individual vote for president matters, because that's simply not the reality of the situation.