Rio hit the nail on the head. Use looped straps with D-shackles. Never use the hitch-ball itself as an attachment point, they can (and do) break and fly off.

If you absolutely must use a strap or chain with hooks make sure the open end of the hook is facing straight up in the air (that way if the hook breaks it will usually fly downwards) and tie some heavy cloth around each end of the strap/rope near the hooks.