It doesn't matter to the compiler (except if your members are data members and their constructors depend on each other), but most people list the publics first, since that's what the people who read your header are most interested in.
As a convention (not a requirement), list your public member first, then protected, then private. The class declarations usually have the following form:
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class SomeClass : public BaseClass
{
public:
...
protected:
...
private:
...
}