If I could summarize SW tanks in a few words I would say "constant balance." Once that is achieved the care for your tank becomes pretty easy.
The process of cycling a tank is a lot easier/faster now because of products that have bacteria in a bottle. Once you understand the import and export part of feeding and the consumption rate of alkalinity, calcium and magnesium, you will be a pro of your individual tank. Salinity will be steady as long as you purchase a "higher" quality Auto top off/osomolator.
For anyone starting the hobby and plans on keeping coral Bulk Reef Supply for supplements is a fair company to buy from. And their reef calculators can be super useful in pinches. I don't care for Kent, brightwell, and any others I did not mention. They have semi complicated instructions that most Newbs can skew their results by miscalculations.
Going back the things I would have liked to change in my first purchases.
1) wish I would have gone to stores like SPS store and seen high end tanks and how to make them look clean with out pumps and overflows obstructing ones view.
2) wish I would have gone to more stores and looked at various styles of set ups to emulate what I wanted and what I didn't want.
3) Take advice with a grain of reef salt. Unless his tanks look like TOTM he can suck it.
4) most important "DONT IMPULSE BUY!" Don't buy on the spot. Research a lot and understand your purchases. Impulse buying can and will cost you more money sometimes wiping out everything you have bought.
5) get to know your lfs owners. What they eat, what type of lettuce they smoke, which hand they slap the banana with. Jk just make sure they aren't Charlatan's, which 80% are. Trust me we all have been duped, but keeping it to controllable damage control is best.
I don't have anything else besides welcome to the most addictive hobby besides punana.