Please do not go for table-space re-org blindly. It will not work for you. You will anyway need double the physcial storage space on your hard disk to do it because database will keep two copies of the tables and tablespace until the re-org is completed and the original tablespace dropped and the new tablespace renamed.
You need to figure out the biggest tables and indexes in this tablespace. Check if you can archive some data out of few large tables. (idocs, log tables , temporary tables etc) . Once you have identified tables from which you can delete/archive data, do it first then re-org those tables.
For indexes, figure out the biggest indexes, which are fragmented ( you can even first try to re-org the 30-40) biggest infdexes and see if you can free some space)
I can go on and on . But please do some research. Start from here and proceed.
706478 - Preventing Basis tables from increasing considerably
Thanks
Amit