I often get asked how to maintain that fresh off the polishing wheel shine on sterling silver. The simple answer is that you can't. You can plate it in rhodium which will keep it really shiny a little longer, but the truth of the matter is that silver is an organic material and it is going to react to it's environment as you wear it. Silver is also an incredibly soft metal and even little things can scratch it.
In fact, sterling work is so susceptible to marks and scratches that once I take it from the polishing wheel I handle it, quite literally, with kid gloves. I clean of the polishing residue using dish-soap and an old piece of super-soft flannel. I try from then on to only handle it using gloves or soft cloths.
That being said, there are ways to keep your silver jewelery looking as good as possible.
The first thing to know is that tarnish, that black film that develops on sterling silver is perfectly normal and DOES NOT mean that you have lousy silver. Sterling silver is made up of 92.5% pure silver, and 7.5% copper. Tarnish is the copper reacting with the air around it. The best thing you can do to protect your sterling it to keep it from air.
The best way to do this is to wear it often! The oils from your skin will actually help to coat and protect your jewelery from the air around it.
When you are not wearing your jewelery, keep it in an airtight container. I recommend small size ziplock bags, 1 piece per bag so they do not scratch each other.
Most anti tarnish devices, be they bags, strips, or waxs work by being impregnated with a chemical that essentially eats the air around them essentially creating a "safe" place for the sterling silver. I hand a strip in my jewelery box, and use cases for my more special pieces (then put those into ziplocks... I am all for extra protection).
So what do you do with pieces you have that are already tarnished? For mild tarnish I do like the jewelery dips although not all jewelers do. For smooth pieces without and nooks and cranies I recommend the Hagardies spray on polish. Bad for the environment? Yep. Good for silver? Oh yeah.
Wait according to the directions, then wipe off with a soft cloth. Wash well to remove all traces of the polish.