It always seems a bit ironic to me that students of Italian put so much effort into learning their grammar, with all its convoluted rules and exceptions, only to be confronted with what appears to be a totally different language when they finally set foot in Italy.
In fact, there is a vast difference between text book Italian and colloquial Italian. Personally I’ve never been much of a grammar book person, and I don’t have much patience for studying verb conjugations and so on, so most of my Italian has been learnt ‘per la strada’. Of course, I have the benefit of Serena’s vast knowledge of ‘correct’ Italian to keep me on line! Naturally, if you don’t live in Italy it’s a lot harder to pick up every day colloquial Italian and attempt to blend in a bit. So to help you out, here’s just a small collection of some of the many colloquial expressions that you’ll hear used a lot in Italy, but probably won’t find in your textbooks:

You’re welcome!
Everyone learns that prego is the typical reply to grazie, don’t they? But in reality it’s only one of the many replies that you’ll hear. Here are a few expressions that all roughly translate as ‘think nothing of it’ or ‘you’re welcome’:

figurati / figuriamoci
ma capirai
non c’è di che
ci mancherebbe (altro)
e di cosa?

Photo (CC) by angela n.

E allora?
Here is a word that you’ll hear all the time. Allora changes its meaning depending on the context and tone of voice:

Allora, cominciamo a mangiare? = Well then, shall we start eating? 
E allora? come va? = so? how is it going?
Allora??? (strong, inquisitorial tone of voice) = So? What’s going on?
Allora!!! (strong, commanding tone of voice) = Stop messing about! / Shut up!
N.B. Allora comes from the Latin ad illam horam (literally: at that time), and we frequently use it with that meaning, e.g.: allora non c’era ancora la televisione (at that time there still wasn’t any television)

I’m cooked!
If you’re feeling very tired, especially mentally tired, here’s a small collection of colourful expressions you might want to try:

sono cotto/a = I’m done (literally: I’m cooked)
sono rimbambito/a = to become like a baby again (literally: I’m re-babyfied).
sono rincoglionito/a = to loose one’s marbles, from coglioni = testicles
sono  rincretinito/a = to become a cretin with tiredness (literally: re-cretinfied)

Odds & Ends
sta a sentire or senti un po’ = listen a moment
stamattina (or stamane), sto pomeriggio, stasera, stanotte= this morning, this afternoon, this evening, tonight (sta and sto are short for questa/o = this)
buondì = gooday N.B. –dì is from the Latin dies = day, e.g. lunedì = Monday (literally: the day of the moon)
ma pensa un po’! / ma tu pensa! = I’d never have thought it!, can you believe it? (literally: but just think about it for a moment!) e.g.: cosa? Mario si è fidanzato con Laura? ma pensa un po’! (what? Mario has got engaged to Laura? can you believe it?
stammi bene (singular), statemi bene (plural) = take care (literally: stay me well)

Allora, cari lettori, statemi bene.