Hey Akhilan Paul,
Visio is a great option to create UML diagrams. I have been using Visio 2010 for the last 9 months for creating various IT diagrams. The following steps will help create UML diagrams easily:
1) Open Microsoft Visio 2010 template
2) On the ribbon, click the File tab, and then click New
3) Click software & database, and then click UML diagram
You can also check the link that I have shared for your reference that will help you understand how to create UML diagrams. There are many pdfs available at www.visiotoolbox.com/2010 which will help you understand how to use Visio.
I am trying relentlessly to get a book explaining UML with Visio 2010. Most of the books speak about Visio 2000 with only a small section on UML or the rest of the books give theoretical knowledge about UML without Visio 2010. Can someone provide me with the name of some book?