Welcome to SEOmoz Dinesh!
There are plenty of ways to build backlinks to your blog, depending on your niche and interests. If you're comfortable with social media, sites like LinkedIn can put you in touch with other professionals in your industry. Although you're going to be doing a ton of guest posting, always be on the lookout for other opportunities. Since you're a beginner, I'll include some fairly easy techniques that can get you started!
Submit to local directories: Don't abuse this and stay away from large generic directories. DMOZ should be a no-brainer (do it) and here's a link to a ton of good quality directories and other sites that accept some form of submission -- http://www.peterattia.com/a-list-of-link-building-lists/
Create some great content: Take the time to create some fantastic content. I try to focus on one piece of content each week that targets an interesting topic and is exceptionally well-written (Take a look at the posts on the SEO Blogs here for an idea of the quality we're talking about). Not only will you need this content for guest posts, but great content tends to get noticed. If you have the skills or budget to create something sharable like an infographic, you can simply use social media outlets to get people excited about your new content, publish it on their sites, and link back to you.
Guest Post: Find people in niches related to yours (the easiest way would be to do a Google search for something like:
Internet marketing + "submit guest post"
Replace "Internet marketing" with a topic of your choice. If you create good content for guest posts, bloggers will be much happier to accept future posts and build a relationship. Don't forget to respond to readers' comments -- this really makes a difference.
Syndicate Your Blog Content to Twitter and Facebook: I use a free tool called Twitterfeed to automatically post all my blogs to Facebook, Twitter, and Google+. It helps you populate your social media feeds effortlessly. Eventually, people notice your content and hopefully start to get interested. You don't get much link value directly from social media sites, but you do have the opportunity to get organic links and readership.
Get Involved: You're doing the right thing right now Dinesh. Get active on online communities and forums. Comment on other posts (sometimes with a no-follow link, sometimes with a do-follow) but make sure your comments actually contribute to or further a discussion already taking place. Don't worry about anchor text here, your site name or personal name is just fine.
As you get better at link building, you won't be able to help finding opportunities wherever you look. No shortage of great advice on the Q & A forum here and in the blogs. Here are some articles past members have written that should give you a solid start:
Good luck to you and happy hunting! You can even send me a message one of these days and discuss some guest posts on my blogs to get started.
Mike
P.S. One very important thing to add. Don't make the mistake of chasing poor metrics like PageRank when valuing a link opportunity on a blog. Check recent posts to see how much interaction there is with the blog community. If you see tons of legitimate comments, that's a great sign.
You're really aiming for traffic, not necessarily rankings. Choose links that will give you traffic and loyal readers, not just links that look good on paper alone.