there are ways to shock it out of fermentation, but the easiest way is to control your sugars prior to fermenting.
I prefer a completely dry product, so the easiest way for me to tell is to wait until it stops bubbling, then i know it is finished! But if you have less sugar to begin with (this is where people use hydrometers), then you will have less food for the yeasts. They will starve themselves out.
Another interesting trick is to go the opposite way. Depending on your selected yeast, they will usually die off around 14 - 16% alcohol. If you have initially more sugars than the yeasts can chomp on, the left-overs will still be in the wine, and you will have a seriously high-octane product. This can also be achieved by fermenting out your wine completely dry (bubbles stopp bubbling), and adding regular flavorless white sugar to taste.
I did a maple-syrup ferment once where I dilluted the mix too much. I fermented it dry, but the flavor was too watery for my tastes. Having not racked it off the yeasties in the mix, i just added more maple syrup and shook it. A day or so later, the bubbles were back.... after that was dry, it was a much better product.