How do you tell someone they are being clingy?

If you are generally a blunt person, you shouldn't have a problem stating your opinion. However, if you aren't blunt, the the best thing to do is say it with no offense, and nicely. If you don't know the person that well, keep the comments to yourself. You don't want to get into a fight with them, and have them claim you don't even kow them. Those words can really get your guard down.