What determines if a particular trait is advantageous to survival?

All you have to do is think about the particular trait, and try to notice is it could branch off, or lead to a way for that certain thing to survive. For example, if I had The great white shark as my topic, then if a trait was intelligent, or clever, I could turn that into a statement that says: " Great White Sharks can use their clever instincts to help them hunt prey." (that was a little vague, but it was an example) So all you have to do is see if you can turn it into a statement similar to that.