I want to ask a question that how many backlinks should i make for my this blog?
Also tell me that building backlins via comments or forums which method is best?
regards

The more backlinks, the better. There can never be enough. It's not just the quantity, though. It's the quality as well.

Personally I don't believe that comments via blog comments or forums work. You just have to create really high quality content that all different types of quality sites will link to in all different ways. Diversity is the key.

we should never stop building backlinks to a site/blog. Both blog commenting and forum posting will work if they are do-follow high page rank sites

I dunno, I disagree cannynimble. I don't think those techniques work anymore. That was sooooooo 2011 :)