Don't forget that you won't be outside for long, so wear a big coat and a pretty dress underneath. But don't wear a full-on Oscars type dress, you'll look a bit daft unless you actually starred in the film.
Pashminas might not be top of the fashion list but they are indespensible. Find a beaded one in netural or complimentary colour and wear it as a wrap .
Plan B and Ive used it depending on your clothes thermal underwear is the way to go!! (that depends on the after party though;)
choose a statement dress, and dont assesorzie. or go for a safe dress and assesorize. always choose one, and never go for something which you dont feel comfortable in. go for long length dresses, and heels are a must.
if its cold wear a small crop jacket or a leather jacket which is always edgy with a formal dress!