What should my engine idle at?

I have a 99 xj sport 6cy and it feels like it idles really low. What should my rpm's be at while it idles?

Idle is 700~750 rpm. Check after engine/transmission have been operated for 20 minutes. Manual in neutral; automatic you need a spare set of hands--set the parking brake, foot on service brakes, place transmission in DRIVE. No a/c running or heavy draws on the alternator--for the AMP freaks out there.