How to update my iPhone without losing all my games progress?

My phone will not stop bothering me to update. Last time I updated it I lost all my games progress and had to start over on everything from angry birds, to hay day, and raising fish was all back to beginning. I followed a couple sites directions but some reason didn't work. What do I do and how do I do it?

Back it up in itunes. Turn off auto syncing in itunes and then update through itunes.