Don't dismiss the Oracle documentation too. Is it much better than previous versions.
Nothing like using EXPLAIN PLAN and TKPROF... whoops i am showing my age as a dba.
If you are using 8i there is an internal package DBMS_PROFILER which will help heaps to timing procedures and functions and finding bottlenecks.
Benchmark the existing process before proceeding to tune. That way you know where to go first (to bottlenecks) and spend time improving code where you will get the greatest return for time spent.
Check out Steve Adam's site as well. It expanded my mind...