The primary approach is to not let your tablespaces get fragmented. If locally managed tablespaces are not available in your version of Oracle then divide your tables/indexes into three groups, by size -- small, medium, large.

Put each type in it's own tablespace -- suggested extent sizes are generally something like 256k, 8m, 256M -- and use pctincrease of 0 on all segments. do not specifyinitial or next when creating segments, just specify the appropriate tablespace based on size.

If locally managed tablespaces are available, then use them. Specify uniform extent sizes, divide the segments into small medium and large as before and put them in an appropiate TS.