Open a telnet session, and run the built-in RIPD-watching commands:
$ telnet localhost 2602
ripd1> show ip rip
ripd1> show ip rip status
ripd1> show work-queues
There are a number of helpful debugging commands as well:
ripd1> enable
ripd1# debug rip zebra
ripd1# debug rip events
The first three commands show routes and all manner of statistics, and the communications between routers. The debug commands show probably more details than you'll ever need to know, but when you're tracking down a problem, they usually pinpoint it quickly.
Quagga documentation: http://www.quagga.net/docs/docs-info.php
/usr/share/doc/quagga