Going in this week for the 20,000 mile check-up. Everytime I go into the dealer they want to sell me things to do to my Prius c. Last time was clean the dust on the brakes and rebalance tires. What are things i need to do at 20,00o to keep the warranty ok and things that I can do or are not necessary to keep warranty valid?
Rotate and balance comes as part of the service during the first 30k here in the US just like oil changes do....
I think your dealer is just trying to get more money out of you. The manual does a pretty good job of telling you what needs to be done. If you have any kind of service contract, check those details as well.
Read your manual and write down or copy the list of required maintenance for 20k miles and take it with you. Tell them that's what you want done, nothing more, nothing less.