Don't Bogart That Joint, My Friend:
http://www.youtube.com/watch?v=EvGJvzwKqg0…

DO "blow out the smoke" to "clear the bong" with your mouth on the stem (where the bowl goes).
DON'T blow down through the top of the bong.

In theory a bong is supposed to be efficient, but smoke left is evidence of waste. Either use a smaller bowel, or don't fill the bowel so full. Personally, I prefer to French inhale off a small hit pipe.

@Dry White Toast: Indeed! Do not fill the bowel so full.

"Do use a vaporizer" Awesome advice. I use my ascent daily, saves me tons of money and herb http://vapesterdam.com/review/ascent-vaporizer-review/

DO not eat the marijuana raw. Good green bud is nearly unchewable and you will have great difficulty swallowing it whole. You will be forced to either spit it out before you are high or you will have to tuck it into your cheek as if it is chaw. If you finally manage the process of mastication or washing the nasty gritty mess down your gullet you may in fact get so high you forget why you have green stains around your mouth and your piss smells like ammonia. Also, marjuana farts from this manner of ingestion are no laughing business. They do not smell like the finest afghan hashish.

Brilliant!

Eating raw Cannabis or Hash doesn't work as well as if it's been baked, because the active ingredients are fat soluble, and need to be processed with a solvent such as butter or oil. Brownies work well, and are especially nice when you've got the munchies. I suppose a chaw could be made by stewing flower shake in olive oil, then dried.

As far as over filling a bowel, an old buddy of mine was a rent-a-freak, in San Francisco, back in the day. Strangers, rich socialites, used to approach him and invite him to their parties provided that he could bring with him some Marijuana.

He used to hang out with the Jefferson Airplane at their apartment where they had a huge hooka. He was a drummer, but not in their band. They would fill the bowel with about an ounce of hash or more and have a big smoke out. Then, they would all go out tripping. That's when my buddy would hesitate to leave, before checking the pipe. Invariably, there would be many grams of unburnt hash left. It seemed to be okay for him to grab a few now and then. Nobody ever told him not to, anyway.