what size wire for household receptacles---14/2 or 12/2

Either one will be acceptable under certain constraints. 12Ga for up to a 20 Amp breaker, ususally for heavy usage appliances. 14Ga for up to a 15 Amp breaker for your average usage. Also, the number of receptacles on the circuit depends on the overall capacity. Be sure to check with the local codes!

I'd use 12/2 with ground. That way you will have adequate wireing for the future. Who thought 30 years ago we'd have all this electronic stuff?