You can also try other off-page optimization tehcniques for getting backlinks such as: directory submision, article, press release submisison, bookmarking, forum posting, blog posting etc...
I think that blog are not high PR or quality full. Go ahead right way you will get backlink. You can also post forums, direcotry, articles etc.
Apart from blog comments you can post in forum sites, two way link exchange and free directory submisison but keep in mind in free directories and in link exchange please use dofollow high PR sites.
You said "blog commenting won't be a very good idea for link building" then why at your tip #5 you said blog posting and forums? and based on the description your put, it looks like you meant blog commenting and not GUEST-POSTING? As for me, Do follow blog or not doesn't really matter as long as ITS MODERATED PROPERLY by the blog owners. Would you consider commenting on a do follow blog with thousands of spammers on it? or commenting on a no follow blog that is moderated and if you got approved you'll get targeted visitors coming to your site.