Your Definitive Election Night Guide

What is going to happen tonight? No one knows. But here’s how it will go down.

Closing time: Polls start closing as early as 6pm, in Indiana, followed by a wave of key states at 8pm and 9pm. The last polls close at 10pm in Nevada and Iowa.

The first numbers: Most states will begin releasing early vote numbers when their polls close. But these numbers do not usually reflect the overall electorate. So a 3-point lead in the early vote does not mean a candidate will win, because it can easily be wiped out as the later votes are tallied. (But a huge lead in early votes might hold.)

Declaring winners: Television news networks generally refrain from projecting winners until all the polls are closed, including the West Coast. Here on the Internet, people can speculate without delay. It is hard, however, to make useful projections based on the early data, which is limited to the early vote and — even less reliable — the exit polls.

Exit polls: The most common source of speculation are the exit polls, which are essentially created by (1) questioning people as they leave the polls today; and (2) calling people who voted early. Exit polls are usually released in waves, and like a weather forecast, they are often in the ballpark but sometimes totally wrong. The early 2004 exit polls showed a decisive victory for John Kerry, for example, which briefly rocked the political and media world. And that was before Twitter.*

Be measured — unless that’s unnecessary: So if you can’t bear to wait for the official projections, the best tack is to be measured while sifting through early indicators. Even that pedantic advice could be wrong, however, since blowouts are usually visible in early data. In 2008, the TV networks refrained from calling the race until 11pm, but the numbers from many key states, including longtime red states, showed a lock on the Electoral College for Obama.

Ultimately, the closer it looks, the less you should believe any early speculations. After all, why believe anyone trying to call a photo-finish without a photo?

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* The A.P., which has a reliable record of projecting election winners since 1848, has instructed its staff not to tweet speculation about winners or to retweet calls by others.