>>>Hi everybody,
>>>
>>>Our log file is getting too big too often. I'm wondering if there are any implications for doing TRUNCATE command quite often and is it possible to setup it as a job?
>>>
>>>Thanks in advance.
>>
>>If you are running regular maintenance jobs (including backup) via SSMS, the log should be getting reset..?
>
>I'm not sure we're running here anything. Can you please tell me what and where exactly should I check?

In SSMS help, look at Maintenance Plans [SQL Server] and Maintenance Plan Wizard under that topic. The wizard is really handy for setting up scheduled maintenance and all the tasks that should be performed.