Does everyone vote at the same time?

No. The US is such a vast country it spans different time zones. The first polling stations close on the East Coast at 7:00pm (midnight UK time), and Alaska is that last at 6am UK time.

What will happen on election night?

Unlike in the UK where we wait avidly for the returning officer to declare a result, US TV stations tend to call each state.

They use partial vote tallies, exit polls and their own projections to call the safer states.

Key moment in the night will be when the polls close in Florida at 7pm EST (12midnight UK time), key swing states Ohio and North Carolina close half an hour later. Another batch of crucial states, including Pennsylvania, close at 8pm (1pm UK time). Colorado and Wisconsin close at 9pm (2am UK), Utah and Iowa close at 10pm EST (3am UK time). It was at this point in 2012 that Barack Obama looked fairly secure, but this race could be a lot tighter.

It is at 11pm EST (4am UK time) polls close in vast California.

What time will the result be declared?

It depends how things are going. Anchors tend not to bother to wait for word from heavily democratic California and its 55 votes if one candidate is far ahead. The best guess is between 4pm and 5pm. But anything could happen.

What should I be looking out for?

A candidate needs at least 270 of the 538 electoral votes to get to the White House. Each state has a different number of votes. All of the television stations will have live interactive maps which will be updated through the night. They will colour in red for the Republicans and blue for the Democrats.

Which states should I look out for?

The key states to look out for are Arizona (11 electoral college votes), Colorado (9), Florida (29), Iowa (6), Nevada (6), New Hampshire (4), North Carolina (15), Ohio (18), Pennsylvania (20) and Virginia (13).

What will a bad night for Hillary Clinton look like?

If she loses the traditional and electoral college rich battlegrounds of Florida and Ohio. Things will start getting uncomfortable for the Clinton camp. She would have to win Pennsylvania and North Carolina and it could make her task that much harder. She will be looking closely at turnout – particularly of Latino voters in Arizona, Florida and Nevada, which have large Hispanic populations and also African-American voters in North Carolina and Ohio.

And what about for Donald Trump?

Mr Trump starts at a disadvantage. If he does not win Florida and Ohio, he can pretty much say farewell to the prospect of a move into the White House. If he wins those two, it is game on, but he would have to win in a raft of other places too.

Which other states should we look out for?

If things do start getting tight, Georgia (with 16 votes), Michigan (16), Utah (6) and Wisconsin (10) will all come into play. Georgia and Utah are Republican strongholds and Michigan and Wisconsin are traditionally Democrat areas – but in this strange election, anything could happen.