Not 100% sure when to use virtual methods in base class

I have a few base classes, and I have derived classes deriving from both bases at the same time. Do I use virtual methods only when I plan on overriding those mehods in the derived classes? I have at least a few methods that are just straight inheritance, the derived classes don't need to override them therefore I did not make them virtual. am I on the right track?

only use them when you intend on performing some "unknown" method with a base class pointer. Otherwise you are wasting the time that it takes to dereference a pointer from a v_ptr table

I tend to make it a rule to make any function that may be implemented differently by a child class virtual. So basically I say yes, you are on the right track.