Just some simple hints:  (still in TODO…)

grep -i 'ERROR:' *.log|lessYou must be in directory with server logs. Command shows you lines with text "error:" (ignores big/small letters). Command "less" is used for pagination - you can list in output using pgdn/ pgup.
grep -i 'ERROR:' -A 3 *.log|lessshows you the same lines as in first example and also 3 following lines.
grep -i 'extra data' *.log|awk ' {print tolower($0)}'|awk 'BEGIN {FS="error:";}{print $2}'|sort|uniq
This construct will show you unique error texts from log files. Just to see what is going on...
for f in *.log; do echo " "; echo $f; grep -i 'error:' $f|awk ' {print tolower($0)}'|awk 'BEGIN {FS="error: ";}{print $2}'|sort|uniq; done|lessThis simple "one-line-script" goes over all log files, displays name of the log file and unique error messages found in it. And makes pagination using "less". Also intended just for quick overview.
grep "execution" cronjob.log |sort -k12 -r|lessThis is a litte bit specialized command for cron jobs log we have. This log has some format and I needed to find slowest logged execution times.