Generally WPPizza will do it’s best to try to automatically determine if caching is being used and tries to ensure the order page is not being cached.
However, it might not always be 100% reliable or possible to determine depending on caching (plugin) used or your host / server settings. If you run into caching issues (like a page/cart being pre-filled with information you know nothing about or indeed not having any items in the cart anymore even if you added them). Ensure that:

• if you are using a cache plugin, you MUST exclude your order page from being cached
• you will also want to enable “I am using a caching plugin” in wppizza->settings
• if your caching plugin does not allow you to exclude certain pages from being cached, use another one
• if your host/server is aggressively caching pages (have a look for something like

  < !-- ....cache generated at ... -->

  or similar in your pages source code, although this might not always exist) , ask them to not cache the WPPizza orderpage url you have set in WPPizza->order settings.