Link acquisition is nothing but gaining links from high qualities sites that provides as a linkback to your own site. For example: Guest posting is a great technique for aquiring high quality do-follow links from other website.
In addition to that, there are many such techniques available being the main motto of getting quality backlinks. Beware to obey guidelines of the search engine in order to sustain yourself on a safer side. Otherwise you will be blush out during the asearch engine's algorithm updates.