Where should I promote my affiliate program?

Warrior forum & Abestweb affiliate forum are great places to start. In fact, any webmaster affiliate or marketing forum would be a good place to start. (don't forget to add it to your signature)

When it comes to affiliate directories, we used these guys and were happy with the results. Unfortunately they are not accepting any new submissions but a search on google and I'm sure you can find a similar service.

Use adwords also. Bid on terms like
- (Product) Affiliate program
- (Product) Associate program

Write a few articles on how to promote affiliate products, how to make money from home promoting other peoples stuff, etc. Use your resource box to promote your affiliate program

Make sure your site has a footer link that links to your affiliate program details/opportunity.

Not sure if you can do this, but being part of more then one 3rd party affiliate program management service opens up the doors to more affiliates. Checkout shareasale.com

If you have the budget, hiring an affiliate program manager is something worth looking into. They will recruit and keep the realtionships strong with your affiliate partners.

Lastly, offer a 2 tiered affiliate program where affiliates can earn a % off the earnings of new referred affiliates into your program.