1. Use non-committal body language before the conversation begins. While it may feel impolite, turning your body away, leaving headphones on, and avoiding eye-contact will signal that you are not in the mood to talk. This may save you from directly telling someone to shut up later on.

Keep working on whatever activity you were doing when they interrupted.
Get up and move around, be active, and find little chores to do instead of listening.

2. Interrupt them as soon as you can. Saying things like, "I'd like to add something," or "If I could interrupt you for just a moment," will often let someone know that they are talking too much. While people often talk quickly, capitalizing on a breath or a brief moment of silence can break the one-sided flow of discussion.

Signal that you would like to speak by holding up your hands, opening your mouth, or clapping. Anything to break their train of thought and get a chance to talk works.

If they ask to finish their thought, don't let them continue to steamroll the conversation; interrupt them once they finish their sentence.

3. Lead the conversation. This is especially helpful when dealing with someone you talk to frequently. Let the person know that you listened to them and steer the discussion in another direction.