the best practices and therefore the best course of action are:
Then check the overall performance of your system. When upgrading from Oracle 10g to 11g it can happen that individual SQL statements show a bad performance, e.g. due to a bad execution plan. Then it is sufficient to analyze and fix them. If you have the SQL Tuning Advisor available, this is an easy task.
If you are interessted in the topic Oracle performance with SAP systems, then have a look at SAP note 618868: FAQ Oracle Performance.
consider also to reorganize tables and to activate compression.
You can compress indexes during reorg freely, while you can compress table too but customer needs to buy "Advanced Compression Option".
Take a look at these notes for more info:
1431800 - Oracle 11.2.0: Central Technical Note
1436352 - Oracle 11g Advanced Compression for SAP Systems
1109743 - Use of Index Key Compression for Oracle Databases
Index Compression allows you to save up to 20% of space, and to improve data buffer quality and database troughput.
Consider that Oracle 11g has a feature (Deferred Segment Creation) that will allow you to save the space occupied by the empty tables.
I like Oracle Compression, it is a good idea to use it, as long as it is included in your license. However compression isn't really part of tuning the database. Typically the performance improvement by compressing the data is too small to be detectable by the dialog users. Some batchjobs might benefit significantly. So don't expect too much from compressing your data. It might happen that you only see temporary effects from the reorganization.
please consider these improvement made by using Advanced Compression (as mentioned on "SAP on Oracle Development Update - November 2011):
Factor 2.2 space savings
60% less physical reads
5% less physical writes
10% better database cache hit rate
30% higher redo rate
No overhead in CPU consumption