best steps and detailed way to reclaim space

Hi ,

What would be the best steps and detailed  way to reclaim space where indexes and tables has many partitions and subpartitions?

We need to reclaim space since we're running out of space on ASM. I cannot resize tablespaces because it already  reached the high watermark. Thank you.

Database version:     10.2.0.1.0 Enterprise Edition

*we don't use enterprise manager

SQL> select NAME, FREE_MB, TOTAL_MB from v$asm_diskgroup;

NAME                              FREE_MB   TOTAL_MB

------------------------------ ---------- ----------

DATADG                               9664     296959