if you asking for decreasing the log file then the only thing you can do is more frequent log backup and execute small chunk of update/insert/delete statement.

Also Shrinking is never the solution for reducing the size....for more understanding of log file have a read of article from Gail:- http://www.sqlservercentral.com/articles/64582/.

Also familiarise yourself about :-

Dbcc sqlperf(logspace)

DBCC loginfo()

select name, log_reuse_wait_desc from sys.databases