i tighten the terminal until snug feeling with the wrench, then a tick more until i can't rotate the terminal by hand.
i also use some kind of dielectric compound on the post and terminal to stop any kind of corrosion caused by out-gassing of the battery.
if i have any of those red and green felt post washers around, i use them with the dielectric compound.
another trick i have used over the years, and it flat out WORKS, is a light spray of wd-40 on the posts and terminals. wipe off the top of the case when done just because.
the wd-40 works as good, and i think BETTER, than those battery sprays and greases available, plus there is no MESS to contend with if you have to disconnect the battery for whatever reason.