UML class diagram: is this how to write abstract method and property?

Every "attribute" is actually a Property in UML2. Abstract methods are displayed by italic text (UML has a boolean value for this).

The notation you are using is called Keyword (simple way) or Stereotype (more complex). If you want to mark a Property as some kind of "special" that's fine with a keyword like you did.

If you're using UMLet to make the UML class you can simply put your class between two forward slashes:

Hope that helps anyone who finds this post and is looking for a way to do it on UMLet.