Evolving

The first thing you need to know is, adding more models will make your account more visible to customers. So, having more models is equal to selling more often.

On top of that, the publishing score will allow your model to outshine and out stand the other models of its own kind, so that way by searching the exact keyword, the customers are directly led to your model. You can achieve that by providing more wireframe renders, polycount and images.
Just like what vivekt478 mentioned.

1. How should I promote my models?
POST LINK ON FB AND TWITTER

2. What should I do to sell models regularly?
KEEP UPLOADING MORE AND QUALITY MODEL

3. How may I show that my models are reliable and quality?
PROVIDE WIREFRAME RENDER AND PLYGON COUNT