I have the fix for one of life's most embarrassing moments. You're at a friend's party, the toilet's clogged, and the water is rising. Here's the advice of Richard Trethewey, a plumbing expert on This Old House. Rather than falling back on your usual 'stare at the toilet and hope for the best' method, do this
Cut the overflow off at the source. Reach down behind the tank and turn the shutoff valve clockwise. You'll usually find that valve to the left of the toilet. Now you can concentrate on the clog. No plunger? No problem. Grab a party cup or a flowerpot and start bailing into the sink.
Once the water level is down, find any kind of plastic bag, slip it up your arm and reach into the abyss. Clear what's clogging the toilet, turn the water back on and give a flush to test for clearance.
Then, give your hand a good scrubbing, go back to the party, and don't breathe a word to anyone.