I have some doubts when to use abstract class and if I need to always code interface. An example:

I have will have series of custom entities, and all of them need to implement SomeMethod() and most of them need to implement AnotherMethod() method.

* SomeMethod() will be entity specific, each entity will have different code.
* AnotherMethod() is implemented by most, but not all, and the code is the same for all.

How is this modeled? My idea is that each new entity must implement SomeMethod() and is able to use AnotherMethod().

Thanks,
Goran