Is this your 'first' second language? If you've learnt another language before you will find it fairly easy to pick up Italian. The good thing about it is that there are many similarities to English and other European languages.

I recommend the Pimsleur tapes for spoken conversation skills and the Teach Yourself series of books.

As for what to learn, obviously the basic greetings but also I find it useful to learn words like 'slice' 'grams' and other supermarket words. Italy's delis are great and there's nothing like fresh sliced proscuitto and cheese on a bread roll for lunch while sitting in the sun

FWIW I learnt Italian at university and had forgotten most of it by the time I finally went to Italy this year! Most useful phrase was -

"vorrei due biglietti per la citta per favore" two tickets to the city please