As mentioned by Littlejon, when finding models I have had the best luck posting on social media accounts, an open casting call or seeking models for a specific project. A friend-of-a-friend is much less likely to flake out than a stranger from MM or Craigslist, and a mutual connection makes it easier to get past that initial communication barrier.
Some things that help:
- Post some examples of your work, ideally in the same style as the project you're looking to shoot.
- Tag the models in your sample images.
- Make sure your post is public so it can be shared and seen.
- Have some references.
- Link to your website, fan page, or portfolio.
- Keep it 100% professional from start to finish.
Here are two examples of posts that I made on my Facebook account, that garnered plenty of responses and shares. Some were from people that I had photographed before, and some were people that I barely knew.
And, to your original question, this resulted in me getting many more contacts for models that I can continue to build relationships with, and call on for future projects.