Employers usually leave time for questions at the end of interviews. Take the opportunity to ask about the timeframe for hiring . Request permission to request an update if you don't hear anything by that date. Planning ahead shows that you're serious about your job and that you're anxious to have a decision. If you have a strong interest in the job, but need a little more time, ask if there is a timeline for making the decision.
If you are interviewing with a large company, ask if the interviewer has any other candidates they are considering and if they have a specific timeline for making a decision. You can also ask if you will hear something by a certain date.