Smoking cigs while high or drunk or on anything, really, is relaxing and much more fun than smoking normally. I know plenty of people who only smoke when they're high or drunk, but when they do, they practically chain em.

Being a smoker myself I mix tobacco with weed to make it go further. A joint is one of the most wasteful ways of smoking weed (though the pros outweigh the cons). If you smoke tobacco anyway, mix em 50 50 (and mix them WELL) and roll medium... never pinner, never too fat. You have to know how to get it really tight, and how to mix them right, or your shit will go out all the time. Burns smoother, lasts longer, wastes less weed smoke inbetween hits.

Tobacco is addictive as hell though. I'm addicted and you will be too if you do it often enough. Avoid mixing unless you're visiting and its the custom (very common in England, and somewhat common in Canada... rarer in the US), or you smoke tobacco already. Doobie and spliff are terms specifically for a mixed roll. Smoker or not, tolerant of nicotine or not, you'll still get a headrush from a spliff, because you hit harder and hold longer when it's weed, than you normally do. Similar with a bong (bong tobacco sometime, it'll knock you on your fuckin' ass)

If you're a nonsmoker looking to conserve the green, try mixing with catnip (careful, it tears papers easily). Catnip doesn't taste bad, sorta tastes like weed really, and gives you a bit of a buzz to boot.