Best way, not sure most folks just bang them on the noggin. It works well. I think it's important to keep fish as fresh as possible. When things die they go South quickly.
No live wells out on the ice , and some folks have ethical concerns about just flipping them on the ice alive.
What one can do is use the ice hole as a live well. I have put my lakers back in the water tail first. 6 inch hole 16 to 30 inches of ice. Hey if they can turn around and swim down to the bottom they are definetly too small and should be let go.
But a decent fish will be in perfect shape at the end of the day. Put your hand in the hole, beach them, bang them on the head and take them home. They won't be swimming in your sink fresh, but they will be the next best thing.
Of course some one is going to come on line now and flame me for not following the Geneva convention for fish. Ohh well. I'm not concerned with the psychological issues a trout may experience, I just like catching and eating them. So if I catch a fish at 10 am and fish to 6 pm I'd rather keep my catch alive until it's time to go home. I'd prefer to put a fresh fish in the pan and not one thats been dead for most of the day.Tail down live well serves that purpose with no harm to the fish.