How to let users mark ( like) other users?
You can use Flag module. It does have integration with Views module. So you can configure and customize.


  Flag is a flexible flagging system that is completely customizable by
  the administrator. Using this module, the site administrator can
  provide any number of flags for nodes, comments, users, and any other
  type of entity. Some possibilities include bookmarks, marking
  important, friends, or flag as offensive. With extensive views
  integration, you can create custom lists of popular content or keep
  tabs on important content.
  
  Flags may be per-user, meaning that each user can mark an item
  individually, or global, meaning that the item is either marked or it
  is not marked, and any user who changes that changes it for everyone.
  
  In this way, additional flags (similar to published and sticky) can be
  put on nodes, or other items, and dealt with by the system however the
  administration likes.