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I like the approach of "Practical UML Statecharts in C/C++", at least the simple one. More or less, keep the state on a function pointer, each state is represented by a function which gets incoming messages or events and returns the next state. I used it for a RS485 protocol running on a microcontroller quite successfully.

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There is also the HSM (hierarchical state machine) extension of this concept (by the same author, not sure it's in the same book) where a given state either handles an event or returns a pointer to a "superstate" that handles it. This kind of "behavioral inheritance" allows for a much more compact code.

Compact and efficient state machines are immensely useful when working with small microcontrollers that don't even run an OS.

The other nice thing about HSMs are concurrent sub-states. They allow clean modeling of the orthogonal aspects of the state.

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