The best SEO activities nowadays are something that produces natural results. It doesn't matter how it is done. For as long as Google is not able to flag the outcome as unnatural, it can be considered as one of the best.
Hi,
All are important for promotion of your site..In that unique article submission,directory submission and forum posting will give good backlinks to your site..
Also, you should use those methods of link building which send traffic to your website, as these methods are good for ranking higher in Google, there is no doubt to it!
The whole off page seo is the process of the link building as mentioned above. All this techniques are good but from that all i prefer social bookmarking and forum posting.