I worked with Wosie with the clicker, and began with sit, then down, then come. I start her from a down position, walk away a few feet, tell her to come, then click and treat when she does. I slowly expanded the distance, and now I go around corners and into other rooms before calling her. Also I have now got her to sit when she gets to me before I click and treat. She's doing well at that, so now I call her to me throughout the day. When she comes to me, I pet and praise her, and sometimes I treat, not always. But it's always one of the happiest things in the world for her to come to me. Never low key, always happy happy happy, and when you tie treats into it, major fun!
Patience and persistence. And treats! Good luck!!