Culture shock from a small company to Big Tech?

First, I highly recommend these 2 discussions:

• "Advice for someone joining big tech from a non big tech background?"
• "Adapting to Big Tech"

Do you have examples and methods how to prepare oneself for those?

It depends a lot on your level:

• If you're junior to mid-level: I would focus on improving your code velocity and quality, which I talk about in-depth here.
• If you're senior or above: The prior point about coding is still important, but now you'll also be expected to do system design and leadership when you go to a Big Tech company. For system design, I recommend my recent System Design series. For the more "soft skill" stuff, there's a big sea of useful resource pointers here.

Usually it's culture shock around how new/different the tooling is, and how many gatekeepers there are.

At a large company, you'll often spend days just waiting for access to certain tables, documents, or tools.