A lot of people feed their salamanders crickets, but if you leave too many in the tank, the crickets will bite them. To death. I lost two sals this way before I learned (from this site) what did it; I just thought they mysteriously died. I'd rather not take the chance and I don't use crickets, but like I said, a lot of people use them; sometimes they stalk and hunt the crickets, which is entertaining. From what I've read.
And if you do use them, make sure they're not to big for the size animal you have.