Best practices to develop projects using dot net technogies

We can't answer that, it's far too broad a subject, and we would need a lot more information about what your project is intended to do, and what market sector it is going into (many of them will have their own rules, regulations, and standards which must be adhered to). Since you also mention "web service" you will also likely have to work within relevant legislation such as GDPR as well.

Start with Google, and work out from there.

It is highly subjective topic and there is no right or wrong way in software development. As suggested by other folks you should do some brainstorming over the topic and get clarity about what problems your application is going to solve, what it is intended to do, its target audiences, input/output, liability on 3rd party services etc.

However, as a starter I would say following things. But, take it with the grain of salt. It is very subjective topic.

If your application is going to be developed as a stand alone windows application then it can be considered as monolithic app. You can use layered architecture in that case.

Create layers for your application as follows
1. Data Layer:- consist of your data CRUD operation
2. Business Layer : Consist of your domain/model classes
3. IOC Layer or DI layer: if you want to implement Dependency Injection
4. (if required) Facade/Proxy layer: to access database or 3rd party service, store info for time being in cache
5. Service layer: for internal data service that can be use
6. Unit test project
7. Main Project:
Views, ViewModels, HelperClasses etc


However, it all depends on what kind of application you are going to create.

You can find plenty of information on internet in respect of requirement.

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