I have yet to see a vehicle that has a convenient, reliable ground point on the frame for boosting. I can't imagine it would cost vehicle manufacturers more than a buck to add one. (Shame!)

That's why people end up using the negative post of the battery as the ground -- even when they know it's not the recommended location.

So, I have reluctantly done it "the wrong way" with evenly matched vehicles and batteries that were only weak, not dead. No problems to report. I'm no expert, but I suspect the trick is to take some time and charge the weak battery at low revs. Then start the weak vehicle, keeping low revs on the charging vehicle. Important safety note in this situation: nobody is allowed anywhere near the batteries when charging or starting is taking place.

But I'm mighty paranoid about "the wrong method," for good reason. Too much juice, in too much of a hurry, with battery-to-battery connections, can be dramatic (and not in a good way). I once witnessed a fellow trying to jump-start a big piece of diesel heavy equipment; he did straight connections, revved his pickup truck up, and blew the caps off that big Cat battery several feet into the air. Yikes!