When do results come in?

11 p.m. UTC: Elections polls close in Kentucky, Indiana, Georgia, South Carolina, Vermont and Virginia close

11:30 p.m. UTC: Election polls close in North Carolina and Ohio    

12 a.m. UTC: Election polls close in Florida, Pennsylvania, New Hampshire and more than 10 other states

1 a.m. UTC: Election polls close in Michigan, Wisconsin, Colorado and more than 10 other states

2 a.m. UTC: Election polls close in Utah and several other states

3 a.m. UTC: Election polls close in California and four other states

4 a.m. UTC: Election polls close in Alaska, the final state

Which are the key states to watch for?

Lee M. Miringoff, director, Marist Institute for Public Opinion at Marist College which conducts the Marist Poll:

"The two states that I am most eager to see the results from are North Carolina and Pennsylvania. Those seem to be the firewall states for Clinton, so if Trump were to score an upset in either of those - and North Carolina is certainly very close now - that means he has avoided getting himself into a deep hole that he may not be able to get out of."

"Florida and Ohio are must-wins for Trump, but not Clinton. She can lose those and still win, but if she wins either of those - Florida or Ohio - there are not a lot of places where he can catch up. Both sides have put enormous amounts of time and money into Florida because for Clinton it's a knock-out punch and for Trump it's a must-win to survive."

Sam Wang, director, Princeton Election Consortium:

"New Hampshire and North Carolina are good early indicators of who is likely to win the election. If Hillary Clinton wins both states she is in a good position to win the race. If Donald Trump wins either or both states, we know that our previous polls are off. It would also mean that he still has some chance to win the election."

"It's fair to say that Trump must win Florida and Ohio to win the election."

What else do I need to know about election night?

It is important to remember that when the winner of a state or the entire race is called by news organizations, it is a projection based on a mix of exit polls and actual votes. It can take much longer until full and final results of the votes are published by the states. 

Even then, the presidential election is not decided by the popular vote, but by the Electoral College vote. Each state is awarded a certain number of Electoral College votes based on the US census, with California having the most electoral votes (55) and states like Delaware (three) having the least. There are 538 electoral votes; a majority of 270 electoral votes is necessary to win the presidential election.