Probably the easiest method would be to drop the tablespace and recreated after moving off any data which resides in the tablespace.
Steps:
1) Make space for existing objects within tablespace (to be dropped) in another tablespace. This might involve using the resize command on existing datafiles if disk space is an issue.
2) Use either CTAS/rename to create temp tables in another tablespace, you could use copy command as well.
3) drop empty tablespace
4) delete OS datafiles
5) recreate tablespace with appropriate sizing
6) Move or recopy tables back into new tablespace.
You will be surprised how fast copy or CTAS commands are. Normally much faster than the equivalent exp/imp methods
Have Fun
Performance... Push the envelope!