How is it determined that a reception or an attack is "perfect" in volleyball? For an attack it is fairly clear it the attack directly scores a point, but there isn't such a clear criterion for receiving.
First of all, there are no definite "rules" for determining the quality of attack or reception. Scouts use certain programs (like this) to collect information about how well players performed in a match but the assessment scheme employed may be different from program to program.
Concerning the attack, yes, scoring is obviously optimal, be it by directly touching the opponent's ground (with the ball, of course), using the block, etc.
With the reception it's somewhat harder as there is no definite "scale" to measure its quality. Teams with an extremely fast-paced play might prefer flat receptions, for example. Anyway, I consider a perfect reception a reception which enables the setter to "do everything" with the ball, that is, play every kind of combination1 with every pace (possibly including an attack by the setter himself/herself). You could use a scale where
0 = disaster; reception directly results in an error 1 = at least playable; some other player except the setter can set the ball 2 = fast play confined; the setter can set the ball but e.g. a fast ball to the middleblocker is hard/impossible 3 = perfect; the setter can play every pace to every player
Here you can find the FIVB statistics from the World Championship 2014. Maybe this gives you a better idea of the assessment of receptions.
1 Alright, you might argue that someone like Luciano de Cecco could play everything from even the base line but we can ignore that, I think.