How to keep friendship alive

A number of times we end up listening to complains from our friends. "You don't call" or "You don't want to keep in touch". Very recently i arrived at the way in which we can keep any relationship alive . It is by doing some activity together.  And something challenging.

Two friends whom i really wanted to stay in touch with , I picked up the activity of cooking with.
We scheduled a day in the week where we would cook something together. Something which one of us did not know. By messaging the item we would build up the excitement for "the day". By doing this it becomes a scheduled thing and we have always something to talk about .