Host templates in Cacti serve a different purpose then data and graph templates. Instead of abstracting the fields of a host, a host template allows you to associate graph templates and data queries with a given host type. This way when you assign a host template to a host, all of the relevant graphs to that host type are only one click away from the user.
To create a new host template in Cacti, select the Host Templates option under the Templates heading. Once on that screen, click Add on the right. Type a unique name for the host template and click the Create button. You will be redirected back to the edit page with the Associated Graph Templates and Associated Data Queries boxes. These two boxes allow you to associate certain graph templates or data queries with the host template. Simply select something from the dropdown menu and click Add to associate it with your host template.