Getting last-minute cancellations can put a black cloud over an event before it has even started. If it's a large, casual cocktail party, then I'll often not say anything until the next day. But if you're not able to make it to a small, seated dinner, you have to call the host - there's nothing worse than an empty chair at a table.

I think the sort of person you want at a party is someone who is self-aware, polite and has a basic knowledge of table manners. And that goes for both men and women.

A good party is one that is designed to entertain and bond friends. The bad parties I've been to are the ones that are held to impress other people.

If it is a cocktail party, I think bringing your partner, husband or wife is fine. To a certain extent, when someone throws a party, they expect to have people over. If it's a seated dinner, though, you should check beforehand. Asking to bring your partner is fair. Asking to bring eight friends from college is not. A good hostess will always accommodate extras and stragglers, but she'll never forget who brought them.

With her first Oscar nomination for her portrayal of Lisbeth Salander in The Girl with the Dragon Tattoo, Rooney Mara gave fashion fans a new Gothic-chic muse.

Talking, texting or tweeting on your phone is the worst in any social situation. I went to a lunch during Paris Fashion Week, and I managed to steal a few moments with Lee Radziwill - who I think is perhaps the classiest woman alive - and she said this is her biggest pet peeve too. So I'm in good company.

Getting last-minute cancellations can put a black cloud over an event before it has even started. If it's a large, casual cocktail party, then I'll often not say anything until the next day. But if you're not able to make it to a small, seated dinner, you have to call the host - there's nothing worse than an empty chair at a table.