There is no official referral programme. It was something Steemit Inc were thinking about a 8 to 9 months back however nothing came of it.
You can refer people using a a referral link in the following format,
https://steemit.com/?r=nanzo-scoop
(changing nanzo-scoop to you username).
I believe this still works.
The Steemit team can then track who signs up using what link. However there has been no communication around how or whether referrals will be remuneration.
We can of course set up our own unofficial referral scheme. For example something along the lines of what I've suggested in this post however it would take buy in from the rest of the community to rewards people that refer others.
Thanks for the info. I was reading up on steem, and must have found an old article when referrals were still being considered.