It's the biggest night of the year in Hollywood - the Oscars begin at 17:30 PST on Sunday (01:30 GMT on Monday) and our live online coverage begins at 23:30.

As the final preparations take place, here's what to look out for in the main battles.

Best picture

Image copyright Lionsgate

The frontrunner: La La Land

Surely, with a record-equalling 14 nominations, this will waltz off with the top award. It's classic yet contemporary. It feels unlike any other modern film, yet feels so right. And it's about the agony and ecstasy of "making it" in Hollywood. What could be more Oscar-friendly?

The challenger: Moonlight

A beautifully-crafted film and a beautifully-told story, Moonlight gives screen time to the type of central character that Hollywood doesn't normally dwell on, or does so only as a stereotype - a poor, young, gay, black, marginalised man.

The outsider: Hidden Figures

This real-life story of three black, female mathematicians in a white, male world at Nasa in the 1960s has exceeded expectations at the US box office, and is the highest-grossing of the nine best picture nominees.

Best actress

Image copyright PA

The frontrunner: Emma Stone (La La Land)

If La La Land is to sweep the board, then it will sweep Emma Stone along with it. She's also at the age, and the stage of her career, at which the Academy likes to admit female stars to its A list.

The challenger: Isabelle Huppert (Elle)

The French actress won a Golden Globe for her role in rape revenge thriller Elle, and there's a strong contingent that thinks the Oscars should give her the credit she deserves for her 40-year career.

The outsider: Natalie Portman (Jackie)

At one stage, Portman and Stone were neck-and-neck. The Academy loves stars who transform themselves into real-life legends, as Portman has with former US first lady Jackie Kennedy. But Jackie has underperformed at the box office and elsewhere in the Oscar nominations.

Best actor

Image copyright Paramount

The frontrunner: Denzel Washington (Fences)

Denzel is probably the marginal favourite in this race. If he wins, he will become only the fourth man to have won three acting Oscars, and will be the oldest best actor winner for 25 years.

Or maybe the frontrunner is: Casey Affleck (Manchester by the Sea)

It's a close call, and Casey is still very much in contention for his depiction of pent-up grief. But he has slipped back, partly because he's hardly charmed the campaign circuit, and partly because of a shadow cast by sexual harassment claims dating back to 2010.

The outsider: Ryan Gosling (La La Land)

If Ryan Gosling wins best actor, then La La Land really will be sweeping everything before it.

Best supporting actress

Image copyright Paramount

The frontrunner: Viola Davis (Fences)

Playing the same role that earned her a Tony Award on Broadway, Viola is, according to the bookies and the pundits, the surest thing in this year's Oscars.

The challengers: Naomie Harris (Moonlight), Nicole Kidman (Lion), Octavia Spencer (Hidden Figures) and Michelle Williams (Manchester by the Sea) all gave fine performances. But they needn't bother rehearsing an acceptance speech.

Best supporting actor

Image copyright A24 Films

The frontrunner: Mahershala Ali (Moonlight)

Ali was the standout performer in Moonlight's ensemble. And with a role in Hidden Figures also among his credits, he is another actor the Academy is ready to anoint as a major star.

The challenger: Dev Patel (Lion)

There's a lot of love and a late surge of support for Patel, who has come of age as an actor eight years after his breakthrough film Slumdog Millionaire won eight Oscars.

The outsider: Jeff Bridges (Hell or High Water)

He may be supporting, but Bridges steals the show as a wizened, maverick Texas Ranger.

Best director

Image copyright Reuters

The frontrunner: Damian Chazelle (La La Land)

La La Land is so beloved by the Academy that they're likely to reward Chazelle's vision and audacity - and the fact he's made a film like this at the age of 32. He would be the youngest best director winner in Oscars history.

The challenger: Barry Jenkins (Moonlight)

But Moonlight also shows rare directorial acumen and marks the arrival of another major film-making talent in Jenkins, who would be the first African-American winner of this award.

The outsider: Mel Gibson (Hacksaw Ridge)

It would be a big statement to give the award to the Australian after his exile from Hollywood following notorious anti-Semitic, racist and misogynist outbursts. But then again, the Oscars did give this award to Roman Polanski in 2003, despite his own Hollywood exile after admitting unlawful sex with a 13-year-old girl.

How many Oscars will La La Land win?

The magical musical has a record-equalling 14 nominations. That includes two for best song - meaning it can win a maximum of 13 statuettes.

The record number of wins in Oscar history is 11 (Titanic, The Lord of the Rings: The Return of the King and Ben-Hur). The record for a musical is 10 (West Side Story).

The hype has cooled a little, so La La Land will do well if it gets into double digits. It's the favourite in 10 of the 13 categories in which it has nominations - the only ones in which it isn't frontrunner are best actor, original screenplay and sound editing.

The most diverse Oscars ever?

After two years of #OscarsSoWhite, in which there were no non-white acting nominees, three of the four acting trophies could go to black actors this year.

If Denzel, Viola and Mahershala all triumph, it will be the first time that black performers will be in the majority when the four acting winners get together for that post-Oscars photo hug.

Who will mention Donald Trump?

A lot of people, probably, directly or indirectly. There's a whole separate article on this.

Image copyright Getty Images

Will Lin-Manuel Miranda get a PEGOT?

There is a select group of 12 people who have got what is known as an EGOT - the set of Emmy, Grammy, Oscar and Tony Awards.

There's an even more select group of just two people (composers Richard Rodgers and Marvin Hamlisch) who have got a PEGOT - all the above plus a Pulitzer Prize.

Lin-Manuel Miranda, who created the Broadway smash Hamilton, currently has a PEGT - he's just missing an O. He's nominated for best song for How Far I'll Go from Moana.

La La Land is hot favourite for that prize, of course. But could the fact it has two nominations in that category split the La La vote and let Lin-Manuel sneak in to complete the set?

Image copyright AMPAS

21st time lucky for Oscar's biggest loser?

Sound recording engineer Kevin O'Connell notched up his 21st Oscar nomination this year for his sound mixing work on Hacksaw Ridge.

That's a great achievement - the shine only coming off it slightly when you consider the fact he's never won.

This could be his year. It could. Except La La Land is standing in his way. So it won't.

At the nominees' luncheon group photo this year, the Academy placed him in the middle, next to the giant Oscars statuette - and the face he made shows he's past caring.

Sibling rivalry for visual effects nominees

Two British brothers are nominated for best visual effects this year, for different films.

Paul Corbould is nominated for Doctor Strange, while Neil Corbould is shortlisted for Rogue One: A Star Wars Story.

Neil has won twice before - for Gladiator and Gravity - while Paul, previously nominated for Guardians of the Galaxy, has never won.

It's a talented family. There's another visual effects wizard brother, Chris, who won an Oscar for Inception. Fortunately for the sake of preventing further family rivalry, he's not nominated this year.

Follow us on Facebook, on Twitter @BBCNewsEnts, or on Instagram at bbcnewsents. If you have a story suggestion email entertainment.news@bbc.co.uk.