Everyone who has surfed Mozilla website perhaps has seen a link that says: Get Involved. This is the simplest way to start helping, to get all the info and the opportunity to find out what you want to help with. This has been my starting point,too. I choose Quality Assurance and, in particular, Desktop Firefox Team. This team is focused on desktop Firefox testing for upcoming major releases and maintenance releases.

Anyway, the first steps to follow starting with Quality Assurance are:

• Set up a Bugzilla account
• Visit the mozilla wiki for how to help, work on some community tasks listed here
• Join IRC on #qa on irc.mozilla.org or other relevant channels. You’ll find other community members, people who will be happy to answer your question and help you.

Some of the first activity to do are :

• Come out to a Testday  joining IRC channel at #testday. More information can be found on the QMO Calendar
• Running developmental builds of Firefox or one of the Firefox channels builds
• Try to Confirm Unconfirmed bugs or Confirm bugs that are marked as fixed and comment the bug to say they are verified. More info are available in the Bugmasters Projects wiki page.  When you have already confirmed 3 or 4 bugs ask for canconfirm or editbug privileges on IRC or follow the indications listed here.
• File bugs to help us improve the product (Some guideline to learn how to file bugs are available here).

More info are available in the doc section Here there are all the info about Events, TestDays, Bugzilla…every thing can help you starting.