This is a great question, (and not just because I wrote a hub way back that answers it but) because you will increase your earning opportunities by encouraging others to write on Hub Pages. The key is including your referral tracker when you send out a link to friends whether by email, facebook, Twitter or other sites. If you have time, please stop by for ideas in answer to your question.
Creating Referral Links for Your Hub Pages Articles by PegCole17 - A few people have found it helpful. If you need specific help, please let me know.
There used to be a way to add a sign-up link to our profiles but that recently changed.