I was NOT fired from my last job, I fear it now though.
This was long before my re-entry for a seasonal position, I voluntarily quit my former job on good terms and wasn't worried about fitting in at all.
Do your work the best you can, and be friendly and helpful, but don't get too close to people until you know you can trust them. Avoid complaining about work AT ALL unless you're sure you can trust the person. You never know who might immediately run to HR and report you for BS things.