Basically, 1964 and older dimes, quarters and halves are silver. You will see a difference when looking at the edges. Some wartime nickels in the 40's were silver and some halves after 64 are 40% silver.
My favorite way is by the sound. Silver and gold have very distinctive pitches when dropped on a hard table top or even just flipped in the air like when you are flipping a coin. Obviously you will want to check the date stamps but if it isn't a coin you can get an idea by it's signature metalic sound. Take some things that you know are gold and silver and try it for yourself to get accustomed to the pitch. I've targeted many silver coins through the years in my change just by paying attention to how they sound. Gold is the same way, a fake ring will have a much duller sound to it due to it's cheaper metal make up, gold will "ring true".