You should use dechlorinator (tap water conditioner) and some form of sea salt mix. Instant Ocean is a pretty good brand, and Red Sea also makes one. The ammount of salt you add depends upon the salinity you wish to achieve. Ask your LFS where you plan to purchase your fish what their salinity is, and match that. You can check your salinities by using a device known as a hydrometer. Red Sea makes one called the SeaTest, and that's what I like to use (when I can't get your hands on a $200 hand held refractomer. Dude, refractometers rock! I should save up and buy me a refractomer just to say I own one).
As for food, variety is the key. I like Ocean Nutrition brands, but there are several others. I try to stay away from flakes, and use that only for quick snacky feedings. Roman lettus and zuchni are a big hit with herbavores, while most carnivores like big fleshy hunks of squid. What you feed is really dependant upon what fish you have, and saltwater fish must have their diet catered to, or else they suffer nutritional defficies really easy.
Some people don't get to check the board but maybe once or twice a day, or week even, so if you don't get an immediate reply, don't panic. It's not that anybody is ignoring you, just that life happens, and it wasn't in front of the computer at that time.
~~Colesea