The major pre-requistes are the desire to become a BA and above average communications skills (oral, written, meeting running, presentation).  Most communication skills can be improved with training and practice.  The latest trend is being a BA in the context of an Agile project.  What is even harder is capturing more permanent information than the "normal"/small/short term Agile project appears to allow.

You can perform the duties/roles of a BA without holding the job title.  You will always be behind in and trying to learn new things to add to your BA knowlege.

There are lots of free webinars available here, at "theIIBA.org" and at Ghanthead.com on various things you need to learn.  Getting a copy of the current version of the BABOK (Business Analysis Book Of Knowlege) would be a good idea.  So would joining the IIBA and a IIBA chapter near you.

Tom Miller, CAPM

Member IIBA