Ask HN: How to Prepare for the Final On-Site Interview?

I passed four rounds of interviews (3 technicals) and the company is now flying me to their HQ for a final on site interview. They said half day.

They didn't give me any details about the agenda so I don't know exactly what to expect. I believe it will be hand shaking, some more tech interviewing and the "culture" test.

Now this is my first time doing an onsite and I don't really know how I should better prepare. Advices?