How to use UML diagrams correctly?

Hello,

I am new here. I have read many articles and tutorials about UML diagrams. I have created few test diagrams as well. From the point of view of developing a software system, which diagram we should develop first and which later? I mean if I have to design a system, how should I start building and finalize the requirement?

Start with use case diagram, from developer view. If you are somehow involved in requirement analysis, then you will also need to understand requirements, they may defined as use cases from customer view! Then you can specify your workflows (if they are not very complex) using activity diagrams.
Ask me again, as soon as you have finilized above tasks. :slight_smile: