In my neck of America (just for anthropological info):
"Smoking weed" refers to cannabis alone, although plenty do mix weed with tobacco. If anyone was planning to mix weed with tobacco, though, it would be mentioned to everyone participating, and would not just be assumed. "Smoking a bowl" implies a pipe OR a bong, and implies only weed. "Smoking a joint" refers to a rolled cigarette but with weed only, no tobacco. "Rolling a spliff" refers to a joint with some amount of tobacco mixed in...this can also be in a verbal form, e.g. "spliffing it" or "spliffing it out" means mixing in tobacco. For most bong users, "smoking a bowl" (if proposed to another smoker) refers to the sharing of a bowl, passing it back and forth. Yes, the smoke has a different taste after the first hit, but much of the effect of hitting pre-burned weed can be diminished by "cornering" the bowl (many bowls have a large enough surface area that a smoker can draw through just one part of the bowl, charring one fraction but leaving the rest green). On a large enough bowl, with judicious cornering, it should be possible to allow four or five smokers to each get a green hit. In any case, the procedure for taking a hit among the people I smoke with would be to fill the bong, pull the slider and clear the bong in one continuous breath. In our etiquette, one lungful is considered a hit, and if you can fill and empty the bong more than once on a single inhalation you are welcome to do so. Of course people have smaller bubblers and also smaller bongs (I have seen smaller bongs with a carb rather than a removable slider and with a bowl size much closer to what I imagine a "cone" to be--in those cases it may be legit to cache the bowl in one hit--do aussies and europeans use the word "cache" for finishing off a bowl?). I have also experienced doing "snappers" (partially-packed bong bowls to be consumed in a single fresh hit), but it is more laborious and time-consuming than just passing a bowl back and forth and so among my friends it is rarer.
