[You cannot use a standard `GET` request.][1]  You must obtain the `access_token` and then `POST` the necessary parameters.

The steps are currently:

**Setup:**

 1. [Register your app.][2]
 2. Link it with [a post here on Stack Apps that has a legitimate \[app\] or \[script\] tag][3].  In most cases you will also tag it with [tag:placeholder].


**In your app:**

 1. Have the user authorize your app and obtain an `access_token` by following the instructions in [the Authentication doc page.][4]  Be sure to include `write_access` in the requested scope.  

  Note that there are two different auth recipes: ***explicit*** and ***implicit***.  
  Which one you are allowed to use is controlled by the ***Client Side Flow*** setting on [your app's registration page (visible only to you)][5].

  If *Client Side Flow* is **Enabled** use the "**implicit**" recipe.  
  Otherwise, use the "explicit" steps.

  For faster and easier code, **use [a library][6] or use [the JavaScript SDK][7]** to handle authentication.

 2. Send a `POST` to 

        https://api.stackexchange.com/2.2/questions/{id}/favorite

  with the following parameters at a minimum:

  `id` =            {The question id -- same as in the POST URL}  
  `key` =           {Your app's key}  
  `site` =          stackoverflow   //-- Or whatever site you're operating on  
  `preview` =       false  
  `access_token` =  {The access token you obtained in step 1}  

 3. On success, the API will return JSON with [a question object][8]. EG:

        {
          "items": [
          ... {question details} ...
          ],
          "has_more": false,
          "quota_max": 10000,
          "quota_remaining": 9996
        }


  [1]: http://stackapps.com/q/4463/7653
  [2]: http://stackapps.com/apps/oauth/register
  [3]: http://stackapps.com/q/4573/7653
  [4]: https://api.stackexchange.com/docs/authentication
  [5]: http://stackapps.com/apps/oauth/
  [6]: http://stackapps.com/questions/tagged/library?sort=votes&pageSize=50
  [7]: https://api.stackexchange.com/docs/js-lib
  [8]: https://api.stackexchange.com/docs/types/question