Demonstrate your talent.
I used to be a cartoonist (yes, you read right) before I got into marketing. And yes, I'm considered to be a darned good copywriter (sure Sean, blow your trumpet), but I couldn't tell you how good I was unless I demonstrated how good I was.
And the demonstration is on the website itself. When customers got to my website or read the Headline Report, they came to their own conclusion--that I was a copywriter.
If only they knew they were dealing with an ex-cartoonist
http://www.psychotactics.com/psychoheadlines.pdf
The headline report
Psychological Marketing Business Tactics: Small Business Ideas
The website (now over 1800 pages wide, but was once just 10 pages)