You can change what Package a class belongs to. Need to add a package?
It is good practice to write an explanation on the background information for this class in the code comment. It will help you remember for what purpose you created it.
The class is often given a default string representation that can be any expression - typically one of its own attributes of type string. Need to add an attribute?
The default string representation is used when a UI tries to display an object of your class without any information about what attribute to show
A class that acts as a superclass for another class is often marked as abstract to indicate that it should not be used directly - this will prohibit creation of objects. You can read more on inheritance in uml here
Objects of classes are normally persistent (they are saved and shared between sessions) but can be made transient (they are short lived in the memory of the current session)