Hi,
Try reading this doc - not particularly long one!
http://www.netapp.com/us/library/technical-reports/tr-3768.html
Ideally logs and DBs should be kept in separate volumes for backup/recovery granularity.
Fractional reserve is a very tricky topic, but the latest recommendation is to keep it at low level (few percent), so SMSQL can delete snapshots when volume is running out of space (on top of that, volume should be set to auto-grow, but that is fairly universal tip these days).
Regards,
Radek