Its effective if your posted content on that website can attract visitors who in turn should visit your blog upon reading your posted content there
it is effective but it will take time to post your articles,you need to ask permission first and wait for the owner's approval,
Yes it is - because it gives you wide platform to post on different blogs with your name and information on it. SEO and Fame both... ways its good
its nothing different with article directory... if its dofollow you will also earn link, traffic for sure if the audience love your article
I would say that guest blogging is a very good way to achieve quality back links and high traffic. Write content for some high PR and high traffic guest blogging sites which provide dofollow links. Links from these sites are every beneficial which are easily considered by Google. And you also get a good amount of referral traffic from these sites.
There are many blogs which allows the guest posts. For example check out this insidermobile.com. But most of the blogs are theme related. if you are good at particular theme then according that you can write and post the content.