Make sure your long term strategy is tied into your short terms tactics.

Tactic - method or technique to achieve a immediate short term gain, run ads, sales calls etc.

Strategy- A carefully defined detailed plan to achieve a long term goal. The overall position you would like to achieve.

So not knowing your long term strategy.. I would venture to focus on having your core customers drive that growth.

Referral programs for existing members to recruit new members get discounts / months off etc. (Think Dropbox)

Run a contest based around your current members that would naturally invite them to share that experience.

This article by Ben Chestnut founder of Mailchimp really embraces the strategy of laser focusing in on current customers.

http://tinyletter.com/ben/letters