You do NOT want one that is timid...runs from you.
Nor do you want one that runs AT you...over agressiveness is best cured in a stew pot.
Either of the two traits above will end up in your gene pool if you breed them. Not good for future generations.
You will want a large bird (not necessarily the largest) that is afraid of nothing. At, or near the top of the pecking order, and no known health issues.
Sixteen weeks is probably too early to make a choice for the best candidate, but certainly old
enough to begin eliminating some. As you see one that is scrawny, weak, timid, unhealthy or otherwise not suitable for your gene pool, it is time to heat up the frying pan. As the weeks pass, you will be down to a few good candidates. That's when the choices become more difficult.
At this point, the hens may actually choose the right one for you. Flock instincts will dictate to the hens which one(s) are best suited to the health and well being of the flock. You may want to keep two. Sometimes a good cock will sacrifice himself to a predator to save the ladies...a true knight. In such a case, if you only have one, you now need to replace him...with somebody else's
reject. When you are down to just a few choices, look for two who get along the best with the ladies,
and each other.
"Breed the best, eat the rest."