I think the first step is to decide what you're interested in learning and reaching out to a project closely aligned with your goals. It is possible you will be rejected, but still worth making the initial effort to find one that would hold your interest. See the following blog post (and comments) explaining the ideal mindset needed when going into this: http://www.hanselman.com/blog/OpenSourceIsAThanklessJobWeDoI...

The specific group that I had in mind was Python; they have implemented a mentorship program at http://pythonmentors.com -- I'd recommend starting there and asking for pointers to other Python projects. With resources like http://learnpythonthehardway.org/ available you should be able to hit the ground running.

Apache maintains a similar process here: https://community.apache.org/mentoringprogramme.html and Debian does too for their package maintainers: https://www.debian.org/doc/manuals/developers-reference/new-...

Google and Facebook both run programs offering opportunity primarily to university students (Summer of Code and Open Academy). You can find a recent study of the Facebook approach here: http://www.sserg.org/the-role-of-mentoring-and-project-chara...

There is also some older info aggregating projects that were looking for help: http://teachingopensource.org/index.php/FOSS_Mentor_Projects

The Outreach Program for Women might not be applicable to you, but there is a lot of good info on their page too: https://wiki.gnome.org/OutreachProgramForWomen