I admit I didn't read all 5 pages of replies before replying, but having been in sales and marketing for many years, so here it is. Borrowing from the U.S. Marine Corps recruiting ads for examples.
1) To earn a customer (recruit), you need to have a compelling product & selling proposition. This is the Who, What, Where, Why and How of your regiment and what it delivers for the potential recruit, i.e., what do they get out of it?
Example:
What NOT to do: Be egotistical and self-serving. "Join MY regiment blah blah blah".
2) You must have a compelling message that is clear, concise, and compelling. Yes, I'm using the word compelling a lot for good reason. The message must be repeated in multiple forms: Forum Post, YouTube video, Forum Signature, Steam Page, Web Page...etc. The message must move the audience member reading/seeing it, (see next item).
Example:
Example of what NOT to do (Marines fail):
3) Visuals > Verbal. People are more moved to action by something they see, rather than a tedious blurb of words.
Example:
4) Deliver on your message. Not only back up your message with consistent content, but also with your & your recruiters' & other leaders' behavior. If you want to be a professional, inspired unit, behave that way. If you want to be an ass-hat unit, behave that way.
5) Last secret: Be exclusive. Scarcity sells. In contrast, desperate pleading (i.e. spamming) for customers/recruits conveys weakness and lack of confidence. Be sure to include a barrier to entry. People are intrigued by barriers and will come flocking over to try your unit out, (see #2 above).
Good luck!