Find a website that has Italian lessons for free. Several are listed in Resources below. A lot of websites want to sell you a package of lessons, but do this only if you're sure it's worth the money. There are plenty of sites that offer free information about learning Italian, including lessons, videos and exercises.
Learn how to pronounce the alphabet and different sounds in Italian. Find a list you can print out that describes how to pronounce all the letters as a guide to refer to. An audio clip of pronunciation is also very helpful here. The eLanguageSchool website has the entire Italian alphabet and pronunciation that you can print out.
Start with simple phrases or common words to work on your pronunciation. By starting to say words out loud that you've heard before, like "grazie," you can perfect your pronunciation of Italian words. Lucio Chiappetti has a great website of words to learn and pronunciation guides for all the sounds.
Find a website that has detailed beginner Italian lessons. These could be videos, audio or written lessons--find the kind that works best with how you learn, or use all three. You'll start by learning words, verbs and nouns and continue by putting them together into sentences. Use a website that has exercises you can complete for practice, like the Italy World Club.
Continue building your Italian vocabulary and find more challenging lessons as you go on. Lots of "learn Italian" websites have beginning and intermediate lessons, so once you find a site you like, keep going through all their lessons regularly. Keep practicing your Italian weekly.