There are several ways to promote your 3D models.
First, generate nice previews of the model and use them to announce new models on your social media accounts, in design forums (not only on CGTrader) and on any portfolio sites.
Always use a direct link to your model page to increase your model's ranking in search engines to have a stronger position in future sales.
As you make a new model, you can film or screenshot the process and upload them as tutorials or ‘How to’ posts with links to the finished project available for sale. Tutorials also help you gain a following and grow your fan base as a 3D artist.
You can promote models directly by generating a unique coupon code for your chosen discount on your models.
Add links to your asset pages in portfolio sites, like Artstation, Behance, DeviantArt, Polycount, Pinterest and others. If you have followers on these sites, they should get notified if you post a link anywhere on those sites. Use a small banner to advertise your shop on CGTrader in any design related page (like a signature with a link in design forums, etc.).
How can I encourage people to download some of my models?
You should always have a simple model available for free download to let potential buyers see your skills. Be sure to use advertising tips in this section, and share your works on design sites and social media to increase your exposure. Generate more reputation and have a good response ratio and response time, to let customers know that you will respond quickly if they need help or support with the model they bought from you.