You could go buy one from a local coin store or you could find one at home. This is more fun than going to a store and buying one. I was fortunate enough to find 3 silver quarters in my 1 year of collecting coins. You may find a silver quarter or you may not.
Step 1: Gather Items
$10 (or more depending on how many rolls you are willing to get)
Step 2: Go to the Bank
Go drive, walk, run, or recumbent bicycle to your local bank. (By the way I do like recumbent bicycles...) Give them your $10 and ask for a roll of quarters. Once you get your quarter roll, go back to your house.
Step 3: Look at the Quarters
Instead of going through the quarters one by one and looking at the dates, look at the edges of the quarters. If you see a ring the color of copper on the edges, they are either copper-nickel clad or silver clad. Silver clad quarters are good too but not as good as the pure silver quarters. If the quarter has no copper ring around it it is silver.
Step 4: Selling Your Silver for Cash
If you decide to sell your silver I would recommend not selling it to a coin dealer because they have to make money too. I recommend selling your silver to an investor or a rookie collector who is just getting started collecting. I have kept all mine for sentimental reasons and they go great in my coin collection.