Silver is very easy to work with, first remember to polish your hammers and working surfaces, clean tools make for clean work. Second get some pickle, a crock-pot or old coffee maker (either one can be used to keep your pickle warm) soap, water and a toothbrush for cleaning flux off the silver from casting or soldering. If you're looking to refine the silver melt it in a crusible with a pinch or two of borax for flux... if your worried about serious impurities: for example say you are using left over casting pieces and bench scraps mixed with filings... then stir the molten silver with a graphite rod and pour it in a steady stream into a steel pot filled with clean cold water, this will give you a fairly refined and workable casting grain, this can then be re-melted and cast as an ingit or into a lost wax mold. If the silver is fairly clean and pure to start then just pour into an ingit mold or lost wax mold. You can make a simple ingit mold by drilling a 1" thick leftover slab of gaphite three-quarters of the way through it's length with a 3/8" drill bit, (it's easier to pour your casting if you counter sink the top of the hole with a 1/2" bit) then cut the graphite slab lengthwise with a bandsaw splitting your drill hole into two equal channels that will create the 2 halves of your ingit mold. Make sure the mold fits together clean without gaps if it has some minor gaps you can carefully sand the pieces so they fit properly. Clamp the mold with C-clamps and pre-heat it with a torch to a few hundred degrees. Flux and melt your silver in a crucible (don't over-flux) then pour it into your mold. Let it cool, release the clamps and check out your ingit (should be a pretty sweet looking piece of silver now.) Pickle it in your crock pot for 10 or 15 minutes then rinse in cold water and clean with your soap and toothbrush, look for pitting or seams that indicate weak areas that may separate during forging. If there are small impurities don't worry you can begin hammering it out into sheet or wire. If it looks bad... or you want another try then re-melt and pour again. When you've got an ingit ready to hammer remember that silver work hardens quickly (much faster than copper) so anneal often, and play it safe to avoid cracking (don't over heat during annealing as it will cause fire-scale in your silver) To anneal silver keep the temperature low: in a perfectly dark room it should just barely glow dark-red at annealing temp, you can quench or air cool silver after reaching annealing temp, air cooling seems to give a little better anneal. Please note that you should never work silver hot unless you want it to crack. At annealing temp or higher silver becomes very brittle it is only soft and maliable when allowed to cool. Ok so that should cover some basics if you have questions send me a message and I'll see if I can help you out. Good luck... I think you should use that piece of silver to make something else... it'll be 100% better when you've made it yourself.
-Eric