[Amahain]

I think with succubi, just do what you like because the appeal isn't the shape of their horns or whether they have cloven hooves or talons, but in what you do with the character.

That said,

1) Tail - to me, that's a must. I like the idea of a prehensile tail; it allows for... options.

2) Claws - of course! Claws and fangs should go without saying.

3) Horns - some might disagree, but I see that as optional. Horns are a good way to illustrate the demonic aspect of the character, but I think you could also go with ridges or bony studs. The one main advantage of horns is that, in written works, they're easier to describe.

4) Hoof/talon thing is also just a matter of preference.