A company wants to see your finished product and they want to see that you're successful. While those qualifications and achievements may be on your resume, it is nice to see your accomplishments first-hand. If you're a writer provide a portfolio, if you're a teacher bring copies of successful curriculums and lesson plans or if you're a scientest bring recent published studies. No matter what your career is there is a way to show proof that you're successful, even if it is merely providing references or letters of recommendation.
There's an old saying that says, "The proof is in the pudding." Make sure your pudding is the best and has all of the ingredients!