Simply ask the player "Is this your first time playing?" the choices to which could be:
- Yes, and I'm new to this sort of game.
- Yes, but I've played this kind of game before.
- No, now shut up and get on with it.
Choice two, tell them to RTFM if they have any questions later.
Choice three, well the answer's obvious then, isn't it.
If they're new but have played this kind of game before, the only parts that need explaining are unusual aspects in the UI and gameplay. (everything else can be skipped)