Most bowhunters today realize the importance of tuning their bows and testing their broadhead flight before hunting. Just because one broadhead flies well doesn't mean that you are done tuning, however.
Three different broadheads from the same package often will fly differently. The cause can be a slightly angled cut to the arrow, a slight angle of the insert, or even a slight imperfection in the broadhead ferrule. Some of these problems can be corrected, and some can be avoided with more care during the arrow-building process.
Such options aren't readily available to the average shooter, however, so the best solution in most cases is to figure out which three or so arrows fly the best with your broadheads, and use those for hunting.
Install your broadheads and give each one the spin test (not on your hand, please) and look for any wobble. Find the arrows that have the least amount of wobble, and you're well on the way to finding your best ones.
Mark your best 6 or so and shoot them until you get your best three (or however many you take to the woods). When you've settled on your best, set those aside until hunting season and continue to practice with the rest of your arrows. Be sure to shoot the "good" arrows a few times right before season to make sure nothing has changed.