As a kid I was in the "steaksauce only" camp. Now, no matter which one I use, it only ruins it.

Salt only: No later than 20 minutes before cooking, or after cooking while it rests, not during. Generally, salting before is better, but if you forget, its still fine to salt during resting. An alternative is to add water and salt to the iron pan where you cooked the steak, reduce, then pour the drippings over the steak.