If you load your ASA ASDM look at realtime log.. have a user vpn in and watch the log you will see IDs and its severity category..
6Sep 25 2009 12:43:24 713228 Group = ciscovpn_ra_access, Username = XXX, IP = xxx.xxx.xxx.xx, Assigned private IP address 10.20.20.20 to remote user
That particular syslog message is ID :713228 , under severity 6 - informational.
for confirming the syslog ID go to syslog IDs link and look at the ID number .
http://www.cisco.com/en/US/docs/security/asa/asa82/system/message/logmsgs.html#wp5391006
for SSL VPN do the procedure above ..
for logging particualr IDs to syslog server use syslog filters.
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/monitor_syslog.html#wp1097397
Jorge Rodriguez