Guest posting would be a effective one but you have to make use of a relevant niche site with high authority. Effective in the sense it would help you to get link authority + views. However it varies with the type of business. some receive huge responses for the videos and press releases.
The most effective off page technique is guest posting and promotion of your content in various Web2.0 platforms. They help to build backlinks and also generate good traffic to rank your keywords higher in search engines.