Do refer to people you do not know well as "pan" (sir) until invited to call them by thier first name.
Don't expect people to speak english just becuase they can. You are living here, learn the language to gain respect.
Do bring taxi money if you are invited to dinner or a party, you probably won't be in any shape to drive when they are through with you.
Don't talk about Solidarity and so forth to older Poles. Most of them prefer things the way they where before 1989. They all had jobs, and crime was low.
Do be prepared to prove every single little detail of your CV.
The poles love documents, red tape, ect. and might even ask for your elementry school grade documents as proof you completed kindergarden if mentioned on your CV.