If the tank isn't leaking, drain it into a portable gas can. If you have an inline filter on it, leave the filter on and drain it through the filter. If not, steal a pair of the Mrs. panty hose and stretch them tight over a funnel and use it to strain out the big chunks.
Let it dry good, then take an air hose and blow everything out till no more debris is seen or heard.
Put it all back together and make sure to put a good inline fuel filter on it.
ALWAYS use STABIL. I put it in my spare gas cans every time so no matter what, my small engines have it in the lines and tank. Another bang for your buck item is "Sea Foam," available at most auto parts stores. Cleans the fuel system out nicely. Any of the Carb or Fuel Injector cleaners or the gas line antifreeze typically contain some denatured alcohol. Denatured alcohol breaks down water and lets it run through the engine without screwing things up.