Developing in Sitecore CMS requires a mix of CMS, .NET, and software development best practices. Here are some key best practices to follow when developing with Sitecore:

1.  Layered Architecture:  

Follow a layered architecture approach (presentation, business, data layer) for separation of concerns. This makes the application more maintainable and testable.

2.  Use Sitecore APIs:  

Always use Sitecore APIs when interacting with Sitecore objects. Direct database reads/writes should be avoided.

3.  Caching:  

Use Sitecore’s caching features to improve performance. However, be careful to clear cache appropriately when content changes.

4.  Rendering and Sub-layout Design:  

Use atomic design principles to build modular and reusable renderings and sub-layouts.

5.  Use MVC:  

As of Sitecore 7.2, Sitecore supports ASP.NET MVC. Using MVC can help you create a clean, well-structured application, particularly when it comes to the presentation layer.

6.  Templates and Inheritance:  

Make good use of Sitecore template inheritance to avoid field duplication, and create a logical, easy-to-understand structure for your content.

7.  Security:  

Follow Sitecore’s security best practices. This includes locking down the Sitecore admin interface, using role-based permissions, and encrypting sensitive configuration settings.

8.  Continuous Integration (CI):  

Implement a continuous integration process to compile, test, and deploy your application.

9.  Versioning and Workflow:  

Use Sitecore’s versioning and workflow features to manage content updates and ensure a smooth content production process.

10.  Analytics:  

Utilize Sitecore’s Experience Analytics for personalization and A/B testing. This allows you to understand your users and tailor the experience to them.

11.  Upgrade Path:  

Keep an eye on your upgrade path. Avoid modifying out-of-the-box Sitecore functionality as much as possible and try to keep customizations isolated. This will help you when it comes time to upgrade to a new version of Sitecore.

12.  Logging:  

Make good use of Sitecore’s logging features. Regularly review and clean your logs to help identify issues and keep your application running smoothly.

13.  Environment-Specific Configuration:  

Use Sitecore’s include files and patching system to manage environment-specific configuration settings.

14.  Training:  

Make sure your team is trained and up-to-date with Sitecore’s features and best practices.

These best practices will help you create a Sitecore application that is reliable, maintainable, and takes full advantage of the power of the Sitecore platform.