This article also appears on Actor's Connection.
Having a good laugh when you're on set can be fun, but every once in a while it's not appropriate. It's important to know when you shouldn't burst out laughing not only because people could get offended, but worse, they could think you don't care about their production.
In general, when you're first starting out on a production and you don't know the crew well, it's best to let things happen and try not to show too many emotions (unless you have to for the scene). The more emotional you are in real life (whether it's laughter, annoyance, anger, or sadness), the more people will form opinions about you. and because you don't necessarily know whether the opinions formed about you will be positive or negative, it's better not to get too involved until you get used to everyone and know who they are and how they think.
I've worked on set where new actors can't seem to get a line right and just burst out laughing in multiple takes. Not only does this look unprofessional, but it can say to the director that you don't take their project seriously. This could lead to your getting fired and even bad word of mouth since there are lots of people on set who are watching you. Some of them could talk to their friends in the industry about you.
Also, be very careful of laughing when someone on set messes something up. I've been on another set where a steadicam operator was running through a field grabbing shots of a war scene, and he tripped and fell over a root. It looked absolutely hilarious, but the camera fell and one of the lenses got damaged. A couple of people laughed when he fell, but the director and primary crew were not amused at all.
They actually seemed really annoyed and disappointed that some people laughed. The behind the scenes videographer actually captured the fall and played it over and over again for people to their amusement, but the steadicam operator approached him and asked him to delete the footage because his career could be completely killed from a mistake like that getting out.
Now all of this isn't to scare you into never laughing on set, but it is to get you consciously thinking about when it's appropriate and when it's not. Since you'll never know for sure, I recommend avoiding laughing during the first few shooting days until you get a sense of the rest of the crew. If everyone else is cracking up and having a good time, by all means, feel free to join. But if the crew seems somber and quiet, it's best not to be the laughing one in the group so you don't stand out in a negative way.