We'll be flying from Berlin to Amsterdam in May, probably on EasyJet. How early should we plan on getting to the airport? Our luggage will be legal carry-on size for U.S.; can we carry it on in Berlin or will it need to be checked?
http://www.easyjet.com/en/help/preparing-to-fly/baggage?link=meganav
This link has your answers to luggage allowances.
For a domestic flight, 2 hours are generally enough time but the same website will have the definitive answer.
1) Berlin has two airports. Know which one you need to go to.
2) Every airline has their own carry on rules. Use the link given in the previous answer to find out the rules for Easyjet. (And with Easyjet, unless you pay extra you don't get a personal item in addition to your carry on.)