....
alter table xxx move;
....
alter index yyy rebuild;
....

ALTER TABLESPACE my_tablespace SHRINK;

ALTER TABLESPACE my_tablespace ENABLE ROW MOVEMENT;

SELECT a.File_Name,
       a.Bytes File_Size_In_Bytes,
       (c.Block_Id + (c.Blocks - 1)) * &_Block_Size hwm_Bytes,
       a.Bytes - ((c.Block_Id + (c.Blocks - 1)) * &_Block_Size) savIng
FROM   dba_Data_Files a,
       (SELECT   File_Id,
                 MAX(Block_Id) Maximum
        FROM     dba_Extents
        GROUP BY File_Id) b,
       dba_Extents c
WHERE  a.File_Id = b.File_Id
       AND c.File_Id = b.File_Id
       AND c.Block_Id = b.Maximum
       AND c.TableSpace_Name = '&tbs_name'

if the value is high,try alter tablespace coalesce and then retry to resize it. 

If your tablespace is LM then there could be no Fragmentation.

SQL> create tablespace tb_test
  2  datafile 'c:\temp\tb_test.dbf' size 100 K autoextend on;
Tablespace created.
SQL> select count(*) from dba_extents where tablespace_name='TB_TEST';
  COUNT(*)                                                                      
----------                                                                      
         0                                                                      
SQL> select bytes from v$datafile where name = 'C:\TEMP\TB_TEST.DBF';
     BYTES                                                                      
----------                                                                      
    106496                                                                      
SQL> create table t_big tablespace tb_test as
  2  select a.* from all_objects a, dba_users for_cartesian;
Table created.
SQL> select count(*) from dba_extents where tablespace_name='TB_TEST';
  COUNT(*)                                                                      
----------                                                                      
        34                                                                      
SQL> select bytes from v$datafile where name = 'C:\TEMP\TB_TEST.DBF';
     BYTES                                                                      
----------                                                                      
  19963904Now we have datafile quite big. Let's drop table and shrink file: 
SQL> drop table t_big;
Table dropped.
SQL> select count(*) from dba_extents where tablespace_name='TB_TEST';
  COUNT(*)                                                                      
----------                                                                      
         0                                                                      
SQL> alter database datafile 'c:\temp\tb_test.dbf' resize 100 K;
alter database datafile 'c:\temp\tb_test.dbf' resize 100 K
*
ERROR at line 1:
ORA-03297: file contains used data beyond requested RESIZE value 
So. even there is nothing reported in DBA_EXTENT, file cannot be shinked. Let's purge recyclebin and try again: 
SQL> purge recyclebin;
Recyclebin purged.
SQL> alter database datafile 'c:\temp\tb_test.dbf' resize 100 K;
Database altered.

SELECT a.File_Name,
       a.Bytes File_Size_In_Bytes,
       (c.Block_Id + (c.Blocks - 1)) * &_Block_Size hwm_Bytes,
       a.Bytes - ((c.Block_Id + (c.Blocks - 1)) * &_Block_Size) savIng
FROM   dba_Data_Files a,
       (SELECT   File_Id,
                 MAX(Block_Id) Maximum
        FROM     dba_Extents
        GROUP BY File_Id) b,
       dba_Extents c
WHERE  a.File_Id = b.File_Id
       AND c.File_Id = b.File_Id
       AND c.Block_Id = b.Maximum
       AND c.TableSpace_Name = '&tbs_name'

SQL> show parameter block_size

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_block_size                        integer     8192
SQL> SELECT a.File_Name,
  2         a.Bytes File_Size_In_Bytes,
  3         (c.Block_Id + (c.Blocks - 1)) * &_Block_Size hwm_Bytes,
  4         a.Bytes - ((c.Block_Id + (c.Blocks - 1)) * &_Block_Size) savIng
  5  FROM   dba_Data_Files a,
  6         (SELECT   File_Id,
  7                   MAX(Block_Id) Maximum
  8          FROM     dba_Extents
  9          GROUP BY File_Id) b,
 10         dba_Extents c
 11  WHERE  a.File_Id = b.File_Id
 12         AND c.File_Id = b.File_Id
 13         AND c.Block_Id = b.Maximum
 14         AND c.TableSpace_Name = '&tbs_name'
 15  /
Enter value for _block_size: 8192
old   3:        (c.Block_Id + (c.Blocks - 1)) * &_Block_Size hwm_Bytes,
new   3:        (c.Block_Id + (c.Blocks - 1)) * 8192 hwm_Bytes,
Enter value for _block_size: 8192
old   4:        a.Bytes - ((c.Block_Id + (c.Blocks - 1)) * &_Block_Size) savIng
new   4:        a.Bytes - ((c.Block_Id + (c.Blocks - 1)) * 8192) savIng
Enter value for tbs_name: HGC
old  14:        AND c.TableSpace_Name = '&tbs_name'
new  14:        AND c.TableSpace_Name = 'HGC'

FILE_NAME
--------------------------------------------------------------------------------

FILE_SIZE_IN_BYTES  HWM_BYTES     SAVING
------------------ ---------- ----------
E:\DATAFILES\HGC01.DBF
        1.5729E+10 3162570752 1.2566E+10