A good rule of thumb is to call after a week or two of silence and ask if you're still being considered for the position. No news is not always good news. Calling can also show you have an interest in the position and lets the employer know you're serious about seeking employment with the company.

If they ask you not to call, then you should probably just not contact, though. Two months of silence is normally a no, and it's actually pretty unprofessional on the company's part. In my opinion it can be a red flag that their management isn't top notch.