There are two main methods that I've found (yes it's very common)
1) Slow way down towards the end. The rate of combuston is controlled by how you draw on the cigar (obviously .. the harder and more often you draw, the faster the stick will burn). If you slow down, it won't burn quite as hot.
2) Purging. BLOW into your cigar (from the head--same place you normally puff from) fairly hard for about 10 seconds or so. Then let the cigar recover for about 30 seconds (you might need to blow on the cherry a bit to keep it going ... that's what she said). Then take another draw, see if it's improved. You may need to purge multiple times, but a good purge will very often return the cigars to the flavors you were enjoying earlier on in the burn.
What purging does (I think) is cause the tar that has built-up during the course of the burn to itself be burned off instead of accumulating near the end and altering the flavors and burn of the cigar.
A lot of people purge often, even before the "hot and squishy" phase at the end, just because some sticks tend to get muddy, bitter, or really strong in the final third. If you don't like that, a purge will usually return you to the flavors of the second third (or thereabouts).
If it's my very first time with a certain cigar, I'll let it burn "as intended." But after that, if I'm not digging it after a while I won't hesitate to purge it--burning cigars are about enjoyment and relaxation, after all, so why not enjoy it? Just yesterday I purged a Padron Anniversary because I wasn't liking it in the final third. That might make Ernesto cringe, but I enjoyed nubbing it afterwards