For a quick easy formula for writing anything, stories, paragraphs or even essays, start with a brainstorming web. 
The whole writing piece can be created from this framework.
The key to this is something called stream of consciousness writing- writing whatever comes to mind on the web:
List anything you can think of and then narrow it down to top 3-4 and number them.  The topic becomes your topic sentence and your top 3 become your 3 supporting sentences or ideas.  Practise brainstorming!!!

---