On a Red Hat-based OS, you can install the RPM by running a command like this:
sudo rpm -ivh avg2012flx-r1786-a4748.i386.rpm
(The i option is for installing, v is for verbosity and h is for a status bar comprised of hash marks.)
After you have it installed, be sure to update your definitions using:
Take a look at the man page for full details, but here is a typical command with my personal favorite set of options:
sudo avgscan -auHd /replace/this/with/your/desired/path
And here's what these options do:
a = Scan inside archives
u = Automatically move infected object to vault
H = Use heuristics for scanning
d = Verbose mode. Multiple -d options increase verbosity. Maximum of 3 options is allowed.
Don't forget, options are case-sensitive! Also, by default avgscan scans recursively through all directories in the path specified unless you specify otherwise. See the man page for details.
I have had very good success with AVG Free for Linux and use it often for scanning USB drives that were inserted into a potentially infected Windows box so have fun!