I havent eaten any of our own chickens yet or any very very old tough ones, but I reckon the ways I cook them should work:
yogurt or buttermilk marinade - soak the whole bird in yogurt or buttermilk for up to 24 hours in the fridge, with some salt and garlic - this really helps tenderize the meat, can roast as normal or on a lower heat for longer
in a dutch oven/
cast iron roaster, put some quartered onions in the bottom, place bird on top, rub bird in and out with olive oil, salt and herbs, stick a quartered lemon inside the bird, then half-fill the pan with white wine or hard
cider, make sure the lid is very tight-fitting (I seal it up with tin foil), and bake in a low temp
oven (130 C or so) for at least 4 hours - I usually put in on in the morning to eat in the evening. if you want some crispy skin you can remove the top and pour off some of the liquid (save it!) and turn the oven up and put the bird back in for 10-15 minutes at the end.
this yeilds really tender chicken and a decent amount of yummy stock that you can save for other things, and I think it would work well with a tougher bird too