Be Friendly, But Professional
What you say and do should ultimately be based on the culture of the place you work and signals from your boss and the celebrity. In some cases, it may not be okay to speak at all, but usually it is alright to at least say something friendly or offer up a simple compliment. Keeping this interaction friendly, succinct, and unassuming can actually help you seem professional and mature in some instances. In some cases, you may even be lucky enough to actually be invited to have a full conversation (and by invited I don't mean they say hi in the hallway, but that your boss actually says something like "Hey Dave, could you come in my office, I want you to meet Selena Gomez." Still, there's always a chance that those you work with would prefer you stick to that old adage about children and be seen but not heard.
If, after evaluating the situation, you do feel the moment is right then:
- Ignore them if they speak to you first
- Act differently than you would talking to anyone else. This also means if you're in a situation where you wouldn't usually say anything then keep that in mind too.
- Go too far in any sense. Don't talk about controversial topics, be too enthusiastic, offer to help with strange things just to be near them, etc.
- Make sensitive jokes that could offend someone even if that type of humor is usually alright in your office
- Talk about press stories
- Talk about their family or significant other
- Use the weather as a reason to start talking to them, it seems to contrived
- Ask for an autograph photo or other way to prove you've met
- Gush about how much you love them
- Stick with simple conversation topics or small talk
- Play it by ear, if you sense the conversation is dying don't try to keep it alive
- Use a compliment or two if appropriate, such as I like your shoes
- Ask if you can get them anything like water or a snack
- Provide directions if needed, for instance if you're in the lobby and a star asks you how to get to the correct suite
- If you truly do like their new song, album, video, etc. offer a straightforward compliment of their work without getting too intense
- Keep your boss updated if the celebrity is coming in to see him or her. Be sure to let your boss know when the star is due to arrive, calls to say they're late, has actually arrived, etc.
- Keep in mind that the rules of what to do and not do can change according to the situation and what the celebrity brings up during a conversation. You can bend the rules if it seems appropriate, but try not to break them.
- Remember that things you see in the office are confidential and use discretion when disclosing anything. It's not okay to tell your friends who came in for a meeting about switching management companies, it's not okay to talk about the new unreleased song you just heard, it's not okay to have your new Facebook status include information about who you just saw roaming the hallways, etc.