While there is an acceptable range of values, here are the numbers I aim for in my setups:

Salinity = 1.025 (specific gravity)
Temperature = 76 – 79 degrees Fahrenheit
pH = 8.3
Alkalinity = 8.5 dKH
Calcium = 430 ppm
Magnesium = 1380 ppm
Ammonia – 0 ppm
Nitrites – 0 ppm
Nitrates = 5 ppm
Phosphates = 0.05 ppm

Saltwater aquarium lighting schedules run about 8 – 12 hours with a 3 – 4 hour photo period in the middle of the schedule. A photo period is when the light is at its most intense point in the schedule.
The nitrogen cycle in an aquarium is the process in which bacterial colonies break down and convert harmful toxins such as ammonia and nitrites into nitrates.
Cycling your aquarium can take anywhere from 2 weeks to 4 months depending on the method used to populate the tank with nitrifying bacteria.

A lot of factors go into this decision, but you can follow this general formula:

(volume of aquarium)/(total inches of fish at mature size) = 3 – 5

Aquarium maintenance is dependent on a few things but typically changing 20% of the aquarium water every two weeks will be sufficient.